Information disc recording/playback apparatus, and vibration detection method for information disc recording/playback apparatus

ABSTRACT

The present invention provides an information disc recording/playback apparatus which includes a track cross detection means ( 112 ), a track cross direction detection means ( 113 ), a rotation angle detection means ( 114 ), and a count means ( 115 ), detects the track pitch of a disc, evaluates the vibration amount, or vibration speed, or vibration acceleration considering the track pitch of the disc, and determines a maximum rotation speed that is lower than the allowable vibration amplitude, vibration speed, or vibration acceleration of the information disc recording/playback apparatus; as well as a vibration detection method for the information disc recording/playback apparatus. This information disc recording/playback apparatus can perform vibration detection using a single threshold value that is independent of the type of the disc, without using an acceleration sensor, and further, the apparatus can accurately perform vibration detection even when direction detection is difficult.

This is a divisional of U.S. application Ser. No. 10/148,808, filed Jun.5, 2002, which is a National Stage Application of InternationalApplication No. PCT/JP01/09934, filed Nov. 14, 2001.

TECHNICAL FIELD

The present invention relates to an information disc recording/playbackapparatus having a vibration measurement means for measuring vibrationscaused by an eccentricity of a disc, and a vibration detection methodfor the information disc recording/playback apparatus. Moreparticularly, the invention relates to an information discrecording/playback apparatus having a construction for performingvibration detection using track counting.

BACKGROUND ART

In recent years, optical disc playback apparatuses have made aremarkable increase in the recording/playback speed. The optical discplayback apparatuses have achieved the increase in the playback speed byincreasing the rotation speed of optical discs.

However, when the rotation speed of an optical disc is increased,vibration due to an eccentricity of the optical disc adversely affectscontrol such as servo, resulting in a problem that the user of theoptical disc playback apparatus might feel uncomfortable. In view ofsuch problem, when an optical disc having a large eccentricity is loadedon the optical disc playback apparatus, the optical disc playbackapparatus limits the rotation speed of the disc to prevent the adverseeffect of vibration due to the disc of the large eccentricity.Therefore, measurement of vibration amplitudes is an important techniquefor preventing the adverse effect of vibration due to the disc of thelarge eccentricity in the optical disc playback apparatus.

FIG. 8 is a block diagram illustrating a conventional optical discplayback apparatus 800 having a structure for detecting vibration withan acceleration sensor. In FIG. 8, reference numeral 801 denotes a base,numeral 802 denotes a disc motor mounted on the base 801, numeral 803denotes an insulator supporting the base 801, numeral 804 denotes a discmounted on the disc motor 802, numeral 805 denotes an accelerationsensor mounted on the base 801, and numeral 806 denotes a measurementunit for measuring the amount of eccentricity on the basis of the outputof the acceleration sensor 805.

Hereinafter, the operation will be described. When the disc motor 802 onwhich the disc 804 is mounted is rotated at a predetermined rpm, acentrifugal force in proportion to the amount of eccentricity of thedisc 804 is generated. The base 801 supported by the insulator 803vibrates at an amplitude that is determined by the amount ofeccentricity of the disc 804, the total mass of the base 801 and theconstituents mounted on the base 801, and the spring constant of theinsulator 803.

The vibration of the base 801 is converted into an electric signal bythe acceleration sensor 805 mounted on the base 801. The measurementunit 806 measures the vibration amplitude of the base 801 on the basisof the electric signal obtained by the acceleration sensor 805.

Then, the measured vibration amplitude is compared with a presetthreshold value, thereby determining a maximum rotation speed of thedisc mounted on the optical disc device.

Furthermore, FIG. 9 is a block diagram illustrating a conventionaloptical disc playback apparatus 900 performing vibration detection usingtrack counting, which is disclosed in Japanese Published PatentApplication No. 2000-113581. In FIG. 9, the same reference numerals asthose shown in FIG. 8 denote the same or corresponding parts, andreference numeral 901 denotes an optical head which is suspended overthe base 801 via an elastic member 902.

Reference numeral 903 denotes a light beam applied to the disc 804 fromthe optical head 901, and numeral 904 denotes information recordingtracks which are concentrically or spirally formed on an informationrecording surface 804A of the disc 804 at a constant pitch. Furthermore,reference numeral 905 denotes a track cross detection unit forgenerating track cross pulses and a cross direction signal from signalswhich are reproduced when the light beam 903 crosses the informationrecording tracks 904; numeral 906 denotes a count unit for counting thetrack cross pulses; numeral 907 denotes a measurement unit fordetermining the amount of eccentricity from the counting result of thecount unit 906; and numeral 908 denotes a motor control unit forcontrolling the rpm of the disc motor 802, and outputting rotation angleinformation to the measurement unit 907.

The distance between the optical head 901 and the disc 804 is keptconstant so that the focus of the light beam 903 is positioned on theinformation recording surface 804A of the disc 804. The position of theoptical head 901 relative to the disc 804 in the direction of the radiusof the disc 804 (the direction indicated by an arrow R) has vibrationcharacteristics represented by a natural frequency of vibration foAwhich is determined by the spring constant of the elastic member 902comprising a material such as metal, resin, or rubber, and the mass ofthe optical head 901.

The base 801 is supported by the insulator 803 comprising a materialsuch as metal, resin, or rubber. When the centrifugal force generated bythe rotation of the disc 804 is propagated through the disc motor 802 tothe base 801, the base 801 vibrates on the basis of vibrationcharacteristics represented by a natural frequency of vibration foMwhich is determined by the total mass of the constituents including thebase 801, the optical head 901 mounted on the base 801, the disc motor802, and the disc 804, and the spring constant of the insulator 803.

The motor control unit 908 rotates the disc motor 802 at a first rpmthat is sufficiently lower than the natural frequency of vibration foA.The optical disc 804 mounted on the disc motor 802 is rotated at thefirst rpm.

Within the range of the first rpm that is sufficiently lower than thenatural frequency of vibration foA, the optical head 901 vibratestogether with the base 801. The relative position between the opticalhead 901 and the optical disc 804 hardly changes. Therefore, at thefirst rpm that is sufficiently lower than the natural frequency ofvibration foA, the light beam 903 crosses a number of informationrecording tracks 904 equivalent to the amount of eccentricity of theinformation recording tracks 904. The light beam 903 generates trackcrosses as many as the information recording tracks 904 the light beam903 has crossed.

Then, the track cross detection unit 905 detects the track crossescorresponding to the information recording tracks 904 the light beam 903has crossed, on the basis of the playback signals of the optical head901, and generates track cross pulses corresponding to the detectedtrack crosses. The track cross detection unit 905 outputs the generatedtrack cross pulses to the count unit 906.

The count unit 906 counts the track cross pulses for one rotation of thedisc 804 on the basis of the rotation angle information from the motorcontrol unit 908. The measurement unit 907 stores a count result N1 ofthe track cross pulses for one rotation of the disc 804, which arecounted by the count unit 906.

Next, the motor control unit 908 rotates the disc motor 802 at a secondrpm that is higher than the natural frequency of vibration foA and lowerthan the natural frequency of vibration foM. Then, a centrifugal forceis generated in the disc 804 due to the eccentricity of the disc 804.The base 801 vibrates at an amplitude that is determined by the amountof eccentricity of the disc 804, the total mass of the base 801 and thecomponents mounted on the base 801, and the spring constant of theinsulator 803.

When the disc motor 802 rotates at the second rpm that is higher thanthe natural frequency of vibration foA and lower than the naturalfrequency of vibration foM, only the base 801, disc motor 802, and disc804 vibrate together while the optical head 901 is in the static state.Therefore, the relative displacement between the disc 804 and theoptical head 901 becomes equal to the vibration displacement of the base801. As a result, the light beam 903 generates track crosses as many asthe tracks equivalent to an amount in which the vibration amplitude ofthe base 801 is added to the amount of eccentricity of the informationrecording tracks 904.

The track cross detection unit 905 detects the track crosses as many asthe tracks equivalent to the amount comprising the amount ofeccentricity of the information recording tracks 904 and the vibrationamplitude of the base 801, and generates track cross pulses as may asthe tracks equivalent to the amount comprising the amount ofeccentricity of the information recording tracks 904 and the vibrationamplitude of the base 801. The track cross detection unit 905 outputsthe generated track cross pulses to the count unit 906.

The count unit 906 counts the track cross pulses for one rotation of thedisc 804, on the basis of the rotation angle information from the motorcontrol unit 908. The measurement unit 907 subtracts the count result N1from a count result N2 obtained by the count unit 906, thereby obtainingthe vibration amplitude of the base 801 alone.

Then, the measured vibration amplitude is compared with a thresholdvalue which is prepared for each disc type, thereby determining amaximum rotation speed of the disc loaded on the optical disc device.

Furthermore, when detecting a vibration amplitude by a track countingmethod, setting of a track count filter according to the vibration speedbecomes important for preventing false count. Although a method ofsetting a track count filter for vibration detection is not general atpresent, a method disclosed in Japanese Published Patent Application No.Hei. 8-45089 is known as a method of setting a track count filter atseeking. To be specific, an optical disc device disclosed is providedwith a PLL circuit for outputting a control frequency according to themoving speed of an optical head when the optical head is moved to atarget track position on the surface of an optical disc by a threadmotor; an F/V conversion circuit for converting the control frequencyinto a voltage; and a ripple detection filter for attenuating a noisecomponent included in a ripple signal from an envelope detectioncircuit, whose filter characteristic is changed according to the voltagefrom the F/V conversion circuit. Thereby, the cut-off frequency of thefilter is varied according to the moving speed of the optical head.

In the above-mentioned conventional method for detecting vibration usingthe acceleration sensor 805, since the vibration itself of the discdevice is measured using the acceleration sensor, a maximum rotationspeed can be determined by comparing the measurement result with asingle threshold value that is independent of the disc type. However, anincrease in cost due to mounting of the acceleration sensor 805 and asignal amplifier for amplifying the signal from the acceleration sensor805 is considerable. Furthermore, it is necessary to secure a space formounting the acceleration sensor 805 and the signal amplifier.

Furthermore, in the conventional method for detecting vibration usingtrack counting, which is disclosed in Japanese Published PatentApplication No. 2000-113581, measurement of vibration amplitudes can becarried out with reduced cost and space, without using an accelerationsensor. However, since track counting is employed, if the track pitch ofthe disc varies, the value of the measured vibration amplitude alsovaries even under the same vibration condition and, therefore, athreshold value must be prepared for each of discs having differenttrack pitches, and a maximum rotation speed is determined by comparisonwith each threshold value. However, the vibration of the disc devicevaries depending on the setting condition of the disc device on asystem, and moreover, the vibration amplitude with which the user feelsuncomfortable depends on the human sense and so it varies depending onthe user. Therefore, a threshold value must be set for each system onwhich the disc device is to be mounted. However, since threshold settingvaries depending on the loading condition or the like of the disc to beused on the disc device, a large amount of data must be measured, andthe amount of data further increases according to the number of disctypes, whereby enormous time is required.

Furthermore, in the method of setting a track count filter disclosed inJapanese Published Patent Application No. Hei. 8-45089, when performingtraverse seek, how the seek speed will change is known in advancebecause acceleration or deceleration of the seek speed is carried outaccording to a speed profile that has previously been determined, andthe response speed to the change in the filter characteristics can beappropriately set according to the predetermined profile. However, inthe case where the frequency and the speed change in the frequency arechanged considerably due to the eccentricity of the disc or thevibration amplitude like the track count pulses for vibration detection,it is difficult to set the response speed to the change in the filtercharacteristics, resulting in false count when the response speed is toohigh or too low.

The present invention is made to solve the above-described problems andhas for its object to provide an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus, which can measure vibration amplitudeswith reduced cost and space without using an acceleration sensor,perform vibration detection using a single threshold value that isindependent of the disc type, and perform accurate vibration detectioneven when direction detection is difficult.

It is another object of the present invention to provide an informationdisc recording/playback apparatus and a vibration detection method forthe information disc recording/playback apparatus, which can provide amethod of controlling the cut-off frequency of a noise removal filterfor track counting most suited to vibration detection, and performaccurate vibration detection with less false count.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

According to a second aspect of the present invention, the informationdisc recording/playback apparatus of the first aspect further comprises:a track cross direction detection means for detecting a track crossdirection indicating the direction in which the reading means crossesthe information tracks; a rotation angle detection means for outputtingrotation angle information of the disc rotation means; and the countmeans for counting the track cross pulses with signs, which are detectedby the track cross detection means, on the basis of the result of thedetection by the track cross direction detection means, and the rotationangle information outputted from the rotation angle detection means.

According to a third aspect of the present invention, the informationdisc recording/playback apparatus of the first aspect further comprises:a track cross direction detection means for detecting a track crossdirection indicating the direction in which the reading means crossesthe information tracks; a track cross speed detection means fordetecting the frequency of the track cross pulses; a rotation angledetection means for outputting rotation angle information of the discrotation means; and the count means for counting the track cross pulseswith signs, which are detected by the track cross detection means, onthe basis of the result of the detection by the track cross directiondetection means and the rotation angle information outputted from therotation angle detection means, while detecting the track crossdirection by the track cross direction detection means when the resultof the detection by the track cross speed detection means indicates thatthe track cross speed is lower than a predetermined value, and countingthe track cross pulses with signs, without detecting the track crossdirection by the track cross direction detection means, on the basis ofthe track cross direction that has just previously been detected by thetrack cross direction detection means, when the result of the detectionby the track cross speed detection means indicates that the track crossspeed becomes higher than the predetermined value.

According to a fourth aspect of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means for counting trackcross pulses with signs, which are detected by the track cross detectionmeans, on the basis of the result of the detection by the track crossdirection detection means and the rotation angle information outputtedfrom the rotation angle detection means, while detecting the track crossdirection by the track cross direction detection means, in an area wherethe track cross speed has the lowest value according to the result ofthe detection by the zero cross area detection means, counting the trackcross pulses with signs, without detecting the track cross direction bythe track cross direction detection means, on the basis of the trackcross direction that has just previously been detected by the trackcross direction detection means, in an area where the track cross speeddoes not have the lowest value according to the result of the detectionby the zero cross area detection means, and outputting the count; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

According to a fifth aspect of the present invention, there is providedan information disc recording/playback apparatus capable of recording orplaying at least two kinds of information discs having different trackpitches, on which information recording tracks are formed spirally orconcentrically, which apparatus comprises: a disc rotation means forrotating the information disc at a predetermined speed; a reading meansfor reading an information signal from the disc; a drive means fordriving the reading means in the direction of the radius of the disc; atrack pitch detection means for detecting the track pitch of theinformation disc from the information disc; a track cross detectionmeans for generating track cross signals on the basis of playbacksignals that are generated when the reading means crosses theinformation tracks; a track cross direction detection means fordetecting a track cross direction indicating the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans, which is divided into n areas for one rotation; a zero cross areadetection means for detecting two areas where the track cross speed hasa lowest value, from among the n areas; a count means including a firstcount means for counting track cross pulses with signs, which aredetected by the track cross detection means, on the basis of the resultof the detection by the track cross direction detection means and therotation angle information outputted from the rotation angle detectionmeans, and a second count means for counting the track cross pulsesdetected by the track cross detection means, without detecting the trackcross direction, on the basis of the rotation angle informationoutputted from the rotation angle detection means, which count meansobtains a first count of the first count means when the drive means isdisabled and the information disc loaded on the disc rotation means isrotated, obtains a second count in which a sign is added to the count ofthe second count means, on the basis of the track cross direction whichhas just previously been detected by the track cross direction detectionmeans, when the drive means is disabled and the information disc loadedon the disc rotation means is rotated, selects the first count in anarea where the track cross speed has the lowest value according to theresult of the detection by the zero cross area detection means, selectsthe second count in an area where the track cross speed does not havethe lowest value according to the result of the detection by the zerocross area detection means, and counts the track cross pulses for everyrotation angle and outputting it; and a control means for determining amaximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus on thebasis of the counts and the track pitch, or determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration speed of the information disc recording/playbackapparatus on the basis of the counts, the track pitch, and the currentdisc rotation speed, and controlling the disc rotation means so that thedisc rotation means rotates the information disc at a speed lower thanthe allowable maximum rotation speed to record or reproduce data in/fromthe disc.

According to a sixth aspect of the present invention, in accordance withthe information disc recording/playback apparatus of the fourth or fifthaspects, the rotation angle detection means divides the rotation angleinformation of the disc rotation means into six areas for each rotation,and outputs the divided information; and the zero cross area detectionmeans detects, as zero cross areas, an area where the count of the countmeans has the smallest value, and an area on a diagonal line withrespect to the area.

According to a seventh aspect of the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing at least two kinds of information discs havingdifferent track pitches, on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track pitch detection means for detecting thetrack pitch of the information disc from the information disc; a trackcross detection means for generating track cross signals on the basis ofplayback signals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for, using, as the count, a differencebetween the track cross count that is obtained when the information discis rotated at a first rotation speed and at least one rotation speedthat is higher than the first rotation speed, and a count that ismeasured with the at least one rotation speed higher than the firstrotation speed, determining a maximum rotation speed that is lower thanan allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

According to an eighth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the seventhaspect, the first rotation speed is a sufficiently low speed at which novibration occurs between the information disc and the reading means, andthe track cross pulses due to the eccentricities of the information discand the disc rotation means are counted.

According to a ninth aspect of the present invention, in accordance withthe information disc recording/playback apparatus of the seventh aspect,the count means counts the track cross pulses at the first rotationspeed for a predetermined number of times, and counts the track crosspulses with the at least one rotation speed that is higher than thefirst rotation speed, for the predetermined number of times; and thecontrol means employs, as the count, an average of counts for more thanone time, which are selected from among the counts obtained by theabove-described repetition, or a value in proportion to the average.

According to a tenth aspect of the present invention, in accordance withthe information disc recording/playback apparatus of the seventh aspect,the rotation angle detection means outputs the rotation angleinformation of the disc rotation means, which is divided into six areasfor one rotation, and when a difference between the track cross countmeasured at the first rotation speed with each of the six-dividedrotation angles, and the track cross count which is measured with the atleast one rotation speed higher than the first rotation speed is asfollows:DAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), the controlmeans determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibration amount 1or a vibration amount 2, or a value in proportion to the second power ofthe vibration amount 1 or the second power of the vibration amount 2,and the track pitch, the vibration amounts 1 and 2 being represented asfollows: $\begin{matrix}{{{vibration}\quad{amount}\quad{1\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 1} \right\rbrack}} + {{DAT}\left\lbrack {n + 1} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 12} \right) \\{{{vibration}\quad{amount}\quad{2\lbrack n\rbrack}} = {\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 2} \right\rbrack}} + {{DAT}\left\lbrack {n + 2} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 13} \right)\end{matrix}$

According to an eleventh aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the tenthaspect, the control means determines a maximum rotation speed that islower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration amounts 1 or vibration amounts 2 whichare calculated for n=0˜5 according to (Formula 12) or (Formula 13), andthe track pitch, or a value in proportion to an average of m pieces ofcentral values selected from among the twelve vibration amounts 1 orvibration amounts 2, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the second powers ofthe twelve vibration amounts 1 or vibration amounts 2, and the trackpitch.

According to a twelfth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the seventhaspect, the rotation angle detection means divides the rotation angleinformation of the disc rotation means into six areas for one rotation,and outputs the divided rotation angle information; and when adifference between the track cross count which is obtained at the firstrotation speed for each of the six-divided rotation angles, and thetrack cross count which is obtained with the at least one rotation speedhigher than the first rotation speed is represented byDAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), and therotation speed of the disc rotation means is Vrpm[rpm], the controlmeans determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibration speed 1or a vibration speed 2, or a value in proportion to the second power ofthe vibration speed 1 or the second power of the vibration speed 2, andthe track pitch, the vibration speeds 1 and 2 being represented by$\begin{matrix}{{{vibration}\quad{speed}\quad{1\lbrack n\rbrack}} = {\frac{2\pi\quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 1} \right\rbrack}} + {{DAT}\left\lbrack {n + 1} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 14} \right) \\{{{vibration}\quad{speed}\quad{2\lbrack n\rbrack}} = {\frac{2\pi\quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 2} \right\rbrack}} + {{DAT}\left\lbrack {n + 2} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 15} \right)\end{matrix}$

According to a thirteenth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the twelfthaspect, the control means determines a maximum rotation speed that islower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration speeds 1 or vibration speeds 2 which arecalculated for n=0˜5 according to (Formula 14) and (Formula 15),respectively, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the values of thetwelve vibration speeds 1 or vibration speeds 2, and the track pitch, ora value in proportion to an average of m pieces of central valuesselected from the second powers of the twelve vibration speeds 1 or thesecond powers of the vibration speeds 2, and the track pitch.

According to a fourteenth aspect of the present invention, in theinformation disc recording/playback apparatus of the seventh aspect, therotation angle detection means divides the rotation angle information ofthe disc rotation means into six areas for one rotation, and outputs thedivided rotation angle information; and when a difference between thetrack cross amount which is measured at the first rotation speed foreach of the six-divided rotation angles, and the track cross amountwhich is measured with the at least one rotation speed higher than thefirst rotation speed is represented byDAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), and therotation speed of the disc rotation means is Vrpm[rpm], the controlmeans determines a maximum rotation speed that is lower than theallowable amplitude of the information disc recording/playbackapparatus, on the basis of a value in proportion to a vibrationacceleration 1 or a vibration acceleration 2, or a value in proportionto the second power of the vibration acceleration 1 or the second powerof the vibration acceleration 2, and the track pitch, the vibrationaccelerations 1 and 2 being represented by $\begin{matrix}{{{vibration}\quad{acceleration}\quad{1\lbrack n\rbrack}} = {\left( \frac{2\pi\quad V_{rpm}}{60} \right)^{2}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 1} \right\rbrack}} + {{DAT}\left\lbrack {n + 1} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 16} \right) \\{{{vibration}\quad{acceleration}\quad{2\lbrack n\rbrack}} = {\left( \frac{2\pi\quad V_{rpm}}{60} \right)^{2}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 2} \right\rbrack}} + {{DAT}\left\lbrack {n + 2} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 17} \right)\end{matrix}$

According to a fifteenth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the fourteenthaspect, the control means determines a maximum rotation speed that islower than the allowable amplitude of the information discrecording/playback apparatus, on the basis of a value in proportion toan average of twelve vibration accelerations 1 or vibrationaccelerations 2 which are calculated for n=0˜5 according to (Formula 16)and (Formula 17), respectively, and the track pitch, or a value inproportion to an average of m pieces of central values selected from thevalues of the twelve vibration accelerations 1 or vibrationaccelerations 2, and the track pitch, or a value in proportion to anaverage of m pieces of central values selected from the second powers ofthe twelve vibration accelerations 1 or the second powers of the twelvevibration accelerations 2, and the track pitch.

According to a sixteenth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of the firstaspect, the track pitch detection means detects the type of the loadedinformation disc, and selects a track pitch corresponding to thedetected disc type, with reference to a table in which standard trackpitches corresponding to the respective types of the information discsare described.

According to a seventeenth aspect of the present invention, theinformation disc recording/playback apparatus of the first aspectfurther comprises: a move distance detection means for detecting thedistance by which the reading means moves; and the track pitch detectionmeans for making the reading means move for a predetermined period oftime or by a predetermined distance when the information disc is loaded,counting the number of tracks the reading means crosses while it ismoving, and detecting the track pitch on the basis of the move distanceand the track cross count.

According to an eighteenth aspect of the present invention, theinformation recording/playback apparatus of the first aspect furthercomprises: a linear speed detection means for detecting the linear speedof the information disc; a a playback speed detection means fordetecting the current playback speed of the information disc; and thetrack pitch detection means for calculating the track pitch of theinformation disc, on the basis of the detected type of the informationdisc, the linear speed of the information disc detected by the linearspeed detection means, the playback speed detected at a predeterminedrotation speed and a predetermined address, the predetermined rotationspeed, the predetermined address, the innermost radius of data areawhich is unique to the detected type of the disc, and the data rate whenthe disc is played at the predetermined playback speed which is uniqueto the type of the disc.

According to a nineteenth aspect of the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing an information disc on which information recordingtracks are formed spirally or concentrically, which apparatus comprises:a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross pulses on the basis of playback signals that aregenerated when the reading means crosses the information tracks; avariable filter means for preventing counting of pulses whose widths arenarrower than a set value, among the track cross pulses; a count meansfor counting the pulses outputted from the variable filter means; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc.

According to a twentieth aspect of the present invention, theinformation disc recording/playback apparatus of the nineteenth aspect,further comprises: a track cross direction detection means for detectingthe track cross direction which indicates the direction in which thereading means crosses the information tracks; a rotation angle detectionmeans for outputting rotation angle information of the disc rotationmeans; and the count means for counting the track cross pulses withsigns, which are detected by the track cross detection means, on thebasis of the result of the detection by the track cross directiondetection means and the rotation angle information outputted from therotation angle detection means.

According to a twenty-first aspect of the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing an information disc on which information recordingtracks are formed spirally or concentrically, which apparatus comprises:a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross pulses on the basis of playback signals that aregenerated when the reading means crosses the information tracks; avariable filter means for preventing counting of pulses whose widths arenarrower than a set value, among the track cross pulses; a track crossdirection detection means for detecting the track cross direction whichindicates the direction in which the reading means crosses theinformation tracks; a rotation angle detection means for outputtingrotation angle information of the disc rotation means; a count meansincluding a first count means for counting the track cross pulses withsigns, which are outputted from the filter means, on the basis of theresult of the detection by the track cross direction detection means andthe rotation angle information outputted from the rotation angledetection means, and a second count means for counting the track crosspulses outputted from the filter means, without detecting the trackcross direction, on the basis of the rotation angle informationoutputted from the rotation angle detection means, which count meansobtains the count of the first or second count means when an initialvalue of count is set for setting an initial value of the variablefilter means, a value of the variable filter is set on the basis of thecount and the current rotation speed, the drive means is disabled, andthe information disc loaded on the disc rotation means is rotated at apredetermined rotation speed, and repeats the process of obtaining thecount of the first or second count means when the value of the variablefilter is set and the information disc is rotated at the predeterminedspeed, for a required number of times, thereby obtaining the counts formore than one rotation; and a control means for determining a maximumrotation speed that is lower than an allowable number of track crossesof the information disc recording/playback apparatus on the basis of thecount, or determining a maximum rotation speed that is lower than anallowable track cross speed or track cross acceleration of theinformation disc recording/playback apparatus on the basis of the countand the current disc rotation speed, and controlling the disc rotationmeans so that the disc rotation means rotates the information disc at aspeed lower than the allowable maximum rotation speed to record orreproduce data in/from the disc.

According to a twenty-second aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thetwenty-first aspect, the count means obtains the count of the firstcount means when the value of the variable filter is set on the basis ofthe count and the current rotation speed, the drive means is disabled,and the information disc loaded on the disc rotation means is rotated ata predetermined rotation speed, and repeats the process of obtaining thecount of the first count means when the information disc is rotated atthe predetermined speed, for a required number of times, therebyobtaining the counts for more than one rotation.

According to a twenty-third aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thetwenty-first or twenty-second aspect, when setting the value of thevariable filter on the basis of the count and the current rotationspeed, if the count is one obtained without detecting the track crossdirection,

assuming that the total number of track crosses per rotation is 4Tc, andthe current rotation speed is Vrpm,

a maximum track cross speed is calculated by $\begin{matrix}{{{maximum}\quad{track}\quad{cross}\quad{speed}} = {\frac{2\pi\quad V_{rpm}}{60}T_{c}}} & \left( {{Formula}\quad 18} \right)\end{matrix}$and, on the basis of the calculated maximum track cross speed, the valueof the variable filter is set, and a minimum track count pulse width isset.

According to a twenty-fourth aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thetwenty-first or twenty-second aspect, the rotation angle detection meansdivides the rotation angle information of the disc rotation means intosix areas for one rotation and outputs the divided rotation angleinformation, and

when the count is one obtained when the track cross direction isdetected, the count at each of the six-divided rotation angles isrepresented byDAT(n)=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), and

the rotation speed of the disc rotation means is Vrpm[rpm],

a value in proportion to a maximum track cross speed 1 or a maximumtrack cross speed 2 which are represented as follows are calculated as amaximum track cross speed, $\begin{matrix}{{{maximum}\quad{track}\quad{cross}\quad{speed}\quad{1\lbrack n\rbrack}} = {\frac{2\pi\quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 1} \right\rbrack}} + {{DAT}\left\lbrack {n + 1} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 19} \right) \\{{{maximum}\quad{track}\quad{cross}\quad{speed}\quad{2\lbrack n\rbrack}} = {\frac{2\pi\quad V_{rpm}}{60}\frac{2}{\sqrt{3}}\sqrt{{{{DAT}\lbrack n\rbrack}^{2} + {{{DAT}\lbrack n\rbrack}{{DAT}\left\lbrack {n + 2} \right\rbrack}} + {{DAT}\left\lbrack {n + 2} \right\rbrack}^{2}}}}} & \left( {{Formula}\quad 20} \right)\end{matrix}$and a value in proportion to an average of twelve maximum track crossspeeds 1 or maximum track cross speeds 2 which are calculated for n=0˜5according to (Formula 19) and (Formula 20), respectively, or a value inproportion to an average of m pieces of central values selected from thevalues of the twelve maximum track cross speeds 1 or maximum track crossspeeds 2, is employed as a maximum track cross speed.

According to a twenty-fifth aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thetwenty-fourth aspect, when the value of the variable filter is set onthe basis of the count and the current rotation speed, if the count isone obtained when the track cross direction is detected, the count ateach of the six-divided rotation angles is represented byDAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), and

the rotation speed of the disc rotation means is Vrpm[rpm],

a maximum track cross speed is calculated on the basis of the followingformulae, $\begin{matrix}{{4T_{c}} = {{{{DAT}\lbrack 0\rbrack}} + {{{DAT}\lbrack 1\rbrack}} + {{{DAT}\lbrack 2\rbrack}} + {{{DAT}\lbrack 3\rbrack}} + {{{DAT}\lbrack 4\rbrack}} + {{{DAT}\lbrack 5\rbrack}}}} & \left( {{Formula}\quad 21} \right) \\{{{maximum}\quad{track}\quad{cross}\quad{speed}} = {{\frac{2\pi\quad V_{rpm}}{60}T_{C}\frac{1}{\cos\quad\frac{\pi}{6}}} = {\frac{2\pi\quad V_{rpm}}{60}T_{C}\frac{2}{\sqrt{3}}}}} & \left( {{Formula}\quad 22} \right)\end{matrix}$and, on the basis of the maximum track cross speed so calculated, thevalue of the variable filter is set, and a minimum track count pulsewidth is set.

According to a twenty-sixth aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thenineteenth aspect, when setting the maximum rotation speed of theinformation disc recording/playback apparatus, the control meansemploys, as the count, a difference between the track cross count thatis obtained when the information disc is rotated at a first rotationspeed and at least one rotation speed that is higher than the firstrotation speed, and the count obtained with the at least one rotationspeed that is higher than the first rotation speed.

According to a twenty-seventh aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thenineteenth aspect, the track cross count is the number of track crosseswhich is calculated on the basis of an average of counts correspondingto more than one rotation, which counts are selected from among thecounts obtained by the repetition.

According to a twenty-eighth aspect of the present invention, inaccordance with the information disc recording/playback apparatus of thetwenty-seventh aspect, when calculating the track cross count, if thevalue of the variable filter means which is reset by repetition at thesame rotation speed changes by a predetermined value or more, the countsobtained before the change are not used as the counts for calculatingthe average.

According to a twenty-ninth aspect of the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing an information disc on which information recordingtracks are formed spirally or concentrically, which apparatus comprises:a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross signals on the basis of playback signals that aregenerated when the reading means crosses the information tracks; a pulsewidth storage means for holding the pulse width of a just-previous trackcross signal; a filter means for comparing the pulse width of thejust-previous track cross signal with the pulse width of the currenttrack cross signal, and preventing the current track cross signal frombeing outputted when the current track cross signal is reduced by apredetermined value or more; a count means for counting the pulses whichare outputted from the variable filter means; and a control means fordetermining a maximum rotation speed that is lower than an allowablenumber of track crosses of the information disc recording/playbackapparatus on the basis of the obtained counts for one or more rotation,or determining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration of the information discrecording/playback apparatus on the basis of the obtained counts for oneor more rotation, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc.

According to a thirtieth aspect of the present invention, in accordancewith the information disc recording/playback apparatus of thetwenty-ninth aspect, the information disc recording/playback apparatusis able to record or play two or more kinds of information discs havingdifferent track pitches; and setting of the maximum rotation speed ofthe information disc recording/playback apparatus is performed bydetecting the track pitch of the information disc, and determining amaximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus on thebasis of the count and the track pitch, or determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration of the information disc recording/playbackapparatus on the basis of the count, the track pitch, and the currentdisc rotation speed.

According to a thirty-first aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of detecting the track pitch of theinformation disc; a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded on the apparatus is rotated and a reading unit crosses theinformation tracks on the information disc, thereby obtaining a count; astep of determining a maximum rotation speed that is lower than anallowable vibration amplitude of the information disc recording/playbackapparatus, on the basis of the obtained count and the track pitch; and astep of determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration of the informationdisc recording/playback apparatus, on the basis of the count, the trackpitch, and the current disc rotation speed.

According to a thirty-second aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of detecting the track pitch of theinformation disc; a step of detecting the track cross directionindicating the direction in which a reading means crosses theinformation tracks; a step of outputting rotation angle information ofthe information disc, which is divided into n areas for one rotation; astep of detecting two areas wherein the track cross speed has the lowestvalue, from among the n-divided areas; a step of counting track crosspulses, which are based on playback signals that are generated when theinformation disc fixedly loaded onto the apparatus is rotated and thereading means crosses the information tracks on the information disc,such that the track cross pulses with signs are counted while detectingthe track cross direction in an area where the track cross speed has thelowest value, on the basis of the detected track cross direction and therotation angle information; a step of counting track cross pulses, whichare based on playback signals that are generated when the informationdisc fixedly loaded onto the apparatus is rotated and the reading meanscrosses the information tracks on the information disc, such that thetrack cross pulses with signs are counted without detecting the trackcross direction, on the basis of the track cross direction which hasjust previously been detected, in an area where the track cross speeddoes not have the lowest value; a step of determining a maximum rotationspeed that is lower than an allowable vibration amplitude of theinformation disc recording/playback apparatus, on the basis of theobtained count and the track pitch; and a step of determining a maximumrotation speed that is lower than an allowable vibration speed orvibration acceleration of the information disc recording/playbackapparatus, on the basis of the count, the track pitch, and the currentdisc rotation speed.

According to a thirty-third aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of detecting the track pitch of theinformation disc; a step of detecting the track cross directionindicating the direction in which a reading means crosses theinformation tracks; a step of outputting rotation angle information ofthe information disc, which is divided into n areas for one rotation; astep of detecting two areas wherein the track cross speed has the lowestvalue, from among the n-divided areas; a step of obtaining a first counton the basis of playback signals which are generated when theinformation disc fixedly loaded onto the apparatus is rotated and thereading means crosses the information tracks on the information disc; astep of obtaining a second count in which a sign is added to the count,on the basis of the track cross direction which has just previously beendetected, when the information disc is rotated; a step of selecting thefirst count in an area where the track cross speed has the lowest value,and selecting the second count in an area where the track cross speeddoes not have the lowest value, thereby counting the track cross pulsesfor every rotation angle and outputting the count; a step of determininga maximum rotation speed that is lower than an allowable vibrationamplitude of the information disc recording/playback apparatus, on thebasis of the obtained count and the track pitch; and a step ofdetermining a maximum rotation speed that is lower than an allowablevibration speed or vibration acceleration of the information discrecording/playback apparatus, on the basis of the count, the trackpitch, and the current disc rotation speed.

According to a thirty-fourth aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing at leasttwo kinds of information discs having different track pitches, on whichinformation recording tracks are formed spirally or concentrically,which method comprises: a step of detecting the track pitch of theinformation disc; a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded onto the apparatus is rotated at a first rotation speed and areading unit crosses the information tracks on the information disc,thereby obtaining a count; a step of calculating a difference between atrack cross count which is obtained when the information disc is rotatedwith at least one rotation speed that is higher than the first rotationspeed, and a count which is obtained when the information disc isrotated at the first rotation speed, thereby obtaining a differencecount; a step of determining a maximum rotation speed that is lower thanan allowable vibration amplitude of the information discrecording/playback apparatus, on the basis of the obtained differencecount and the track pitch; and a step of determining a maximum rotationspeed that is lower than an allowable vibration speed or vibrationacceleration of the information disc recording/playback apparatus, onthe basis of the difference count, the track pitch, and the current discrotation speed.

According to a thirty-fifth aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing aninformation disc on which information recording tracks are formedspirally or concentrically, which method comprises: a step of countingtrack cross pulses on the basis of playback signals which are generatedwhen the information disc fixedly loaded on the apparatus is rotated anda reading unit crosses the information tracks on the information disc,thereby obtaining a count; a step of comparing the widths of thedetected track pulses with a predetermined value, and invalidating thecounts of track pulses whose widths are shorter than the predeterminedvalue; a step of determining a maximum rotation speed that is lower thanan allowable number of track crosses of the information discrecording/playback apparatus, on the basis of the count; and a step ofdetermining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration, on the basis of the countand the current disc rotation speed.

According to a thirty-sixth aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing aninformation disc on which information recording tracks are formedspirally or concentrically, which method comprises: a step of countingtrack cross pulses on the basis of playback signals which are generatedwhen the information disc fixedly loaded on the apparatus is rotated anda reading unit crosses the information tracks on the information disc,thereby obtaining a count; a step of detecting the track cross directionindicating the direction in which the reading means crosses theinformation tracks; a step of outputting rotation angle information ofthe information disc; a step of comparing a set pulse width with thepulse width of the current track cross pulse, and invalidating the countof the current track cross pulse when its pulse width is decreased by apredetermined value or more; a first count step of counting the trackcross pulses with signs, whose widths are not decreased by thepredetermined value or more, on the basis of the track cross directionand the rotation angle information; a second count step of counting thetrack cross pulses whose widths are not decreased by the predeterminedvalue or more, without detecting the track cross direction, on the basisof the rotation angle information; a step of setting the set pulsewidths by repeating the steps of obtaining the first and second countsby a required number of times; a step of obtaining a count correspondingto one or more rotation of the information disc, by obtaining the countsobtained in the first and second count steps using the repeatedly setpulse widths; a step of determining a maximum rotation speed that islower than an allowable number of track crosses of the information discrecording/playback apparatus, on the basis of the count; and a step ofdetermining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration, on the basis of the countand the current disc rotation speed.

According to a thirty-seventh aspect of the present invention, there isprovided a vibration detection method for an information discrecording/playback apparatus capable of recording or playing aninformation disc on which information recording tracks are formedspirally or concentrically, which method comprises: a step of countingtrack cross pulses on the basis of playback signals which are generatedwhen the information disc fixedly loaded on the apparatus is rotated anda reading unit crosses the information tracks on the information disc,thereby obtaining a count; a step of storing the pulse width of a trackcross pulse which has just previously been detected; a step of comparingthe stored track cross pulse width with the pulse width of the currenttrack cross pulse, and invalidating the count of the current track crosspulse when its pulse width is decreased by a predetermined value ormore; a step of determining a maximum rotation speed that is lower thanan allowable number of track crosses of the information discrecording/playback apparatus, on the basis of the count; and a step ofdetermining a maximum rotation speed that is lower than an allowabletrack cross speed or track cross acceleration, on the basis of the countand the current disc rotation speed.

As described above, according to an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus relating to the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing at least two kinds of information discs havingdifferent track pitches, on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track pitch detection means for detecting thetrack pitch of the information disc from the information disc; a trackcross detection means for generating track cross signals on the basis ofplayback signals that are generated when the reading means crosses theinformation tracks; a count means for counting track cross pulses thatare detected by the track cross detection means, and outputting thecount; and a control means for determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration speed of theinformation disc recording/playback apparatus on the basis of the count,the track pitch, and the current disc rotation speed, and controllingthe disc rotation means so that the disc rotation means rotates theinformation disc at a speed lower than the allowable maximum rotationspeed to record or reproduce data in/from the disc. Therefore, thevibration amplitude, or vibration speed, or vibration acceleration isevaluated considering the track pitch of the disc, and the maximumrotation speed lower than the allowable vibration amplitude, orvibration speed, or vibration acceleration of the information discrecording/playback apparatus is determined, whereby vibration detectioncan be carried out using a single threshold value, regardless of thetype of the information disc.

Furthermore, according to an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus relating to the present invention, there isprovided an information disc recording/playback apparatus capable ofrecording or playing an information disc on which information recordingtracks are formed spirally or concentrically, which apparatus comprises:a disc rotation means for rotating the information disc at apredetermined speed; a reading means for reading an information signalfrom the disc; a drive means for driving the reading means in thedirection of the radius of the disc; a track cross detection means forgenerating track cross pulses on the basis of playback signals that aregenerated when the reading means crosses the information tracks; avariable filter means for preventing counting of pulses whose widths arenarrower than a set value, among the track cross pulses; a count meansfor counting the pulses outputted from the variable filter means; and acontrol means for determining a maximum rotation speed that is lowerthan an allowable number of track crosses of the information discrecording/playback apparatus on the basis of the count, or determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration of the information disc recording/playbackapparatus on the basis of the count and the current disc rotation speed,and controlling the disc rotation means so that the disc rotation meansrotates the information disc at a speed lower than the allowable maximumrotation speed to record or reproduce data in/from the disc. Sincesetting of the track cross filter is carried out on the basis of thetrack cross count and the current rotation speed, even when the trackcross speed varies significantly due to the eccentricity or vibration ofthe disc, track counting most suitable for vibration detection can beaccurately carried out at all times.

Furthermore, according to an information disc recording/playbackapparatus relating to the present invention, there is provided aninformation disc recording/playback apparatus capable of recording orplaying an information disc on which information recording tracks areformed spirally or concentrically, which apparatus comprises: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross signals on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a pulse width storagemeans for holding the pulse width of a just-previous track cross signal;a filter means for comparing the pulse width of the just-previous trackcross signal with the pulse width of the current track cross signal, andpreventing the current track cross signal from being outputted when thecurrent track cross signal is reduced by a predetermined value or more;a count means for counting the pulses which are outputted from thevariable filter means; and a control means for determining a maximumrotation speed that is lower than an allowable number of track crossesof the information disc recording/playback apparatus on the basis of theobtained counts for one or more rotation, or determining a maximumrotation speed that is lower than an allowable track cross speed ortrack cross acceleration of the information disc recording/playbackapparatus on the basis of the obtained counts for one or more rotation,and the current disc rotation speed, and controlling the disc rotationmeans so that the disc rotation means rotates the information disc at aspeed lower than the allowable maximum rotation speed to record orreproduce data in/from the disc. Therefore, when the current pulse widthis smaller than the previous pulse width by a predetermined value, thispulse is judged as one caused by false detection due to noise and is notcounted, whereby track counting most suitable for vibration detectioncan be accurately carried out at all times, without requiring time forexcess measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a first or fourth embodimentof the invention are applied to the DVD-ROM player.

FIG. 2 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a second embodiment of theinvention are applied to the DVD-ROM player.

FIG. 3 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a third embodiment of theinvention are applied to the DVD-ROM player.

FIG. 4 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a fifth embodiment of theinvention are applied to the DVD-ROM player.

FIG. 5 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a sixth, seventh, or eighthembodiment of the invention are applied to the DVD-ROM player.

FIG. 6 is a diagram illustrating a graph showing the amount ofdisplacement of the count at every rotation angle, which displacement iscaused by vibration or eccentricity, when the present invention isapplied to the DVD-ROM player.

FIG. 7 is a block diagram illustrating the construction of a DVD-ROMplayer in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to a ninth embodiment of theinvention are applied to the DVD-ROM player.

FIG. 8 is a block diagram illustrating the construction of aconventional optical disc playback apparatus which performs vibrationdetection using an acceleration sensor.

FIG. 9 is a block diagram illustrating the construction of aconventional optical disc playback apparatus which performs vibrationdetection using track counting.

FIG. 10 is a block diagram illustrating the construction of anotherDVD-ROM player in the case where an information disc recording/playbackapparatus and a vibration detection method for the information discrecording/playback apparatus according to the fifth embodiment of theinvention are applied to the DVD-ROM player.

BEST MODE TO EXECUTE THE INVENTION EMBODIMENT 1

An information disc recording/playback apparatus and a vibrationdetection method for the information disc recording/playback apparatusaccording to a first embodiment of the present invention will bedescribed taking a DVD-ROM player as an example, with reference to FIG.1.

In FIG. 1, a DVD-ROM player 101 is able to play various kinds of opticaldiscs 102. The DVD-ROM player 101 according to this first embodiment isable to play the following discs: CD-ROM (CD-ROM, CD-R, CD-RW), DVD-ROM(DVD-5, DVD-9, DVD-R4.7 G), and DVD-R3.9 G, and the standard trackpitches of these discs are as follows: CD-ROM  1.6 μm DVD-ROM 0.74 μmDVD-R3.9G 0.80 μm

Reference numeral 103 denotes a disc rotation means for rotating theoptical disc 102 mounted on the DVD-ROM player 101 at a predeterminedrpm. Reference numeral 104 denotes a reading means for reading aninformation signal from the optical disc 102. In the DVD-ROM player 101,the reading means 104 comprises, for example, a laser emission element105 for emitting two laser beams having different oscillationwavelengths, one for a CD-ROM and the other for a DVD-ROM; an objectivelens 106 for converging the laser beams; and a two-element photodetector107, one for a CD-ROM and the other for a DVD-ROM. The reading means 104amplifies the outputs from the photodetector 107, selects one of theoutput signals from the photodetector 107 according to the type of theoptical disc 102, generates a tracking error (TE) signal, a focus error(FE) signal, a playback signal (RF), an All Sum signal (AS), an RFenvelope signal (RFENV) and the like, and outputs these signals.

Reference numeral 108 denotes a conversion means for converting theplayback signal outputted from the reading means 104 into digital data.Reference numeral 109 denotes a drive means for driving the readingmeans 104 in the direction of the radius of the optical disc 102. Thisdrive means 109 comprises, for example, a traverse drive means 110 fordriving the whole reading means 104 in the direction of the radius ofthe optical disc, and a tracking actuator 111 for minutely driving theobjective lens 106 included in the reading means 104, in the directionof the radius of the optical disc.

Reference numeral 112 denotes a track cross detection means forgenerating track cross pulses on the basis of playback signals which aregenerated when the laser beam outputted from the reading means 104crosses the tracks on the optical disc 102. Reference numeral 113denotes a track cross direction detection means for detecting thedirection along which the laser beam from the reading means 104 crossesthe tracks on the optical disc. The track cross detection means 112 orthe track cross direction detection means 113 binarizes the trackingerror signal outputted from the reading means 104 with a hysteresiscomparator or a comparator to generate a track count signal TKC.Likewise, the track cross detection means 112 or the track crossdirection detection means 113 generates a non-on track signal OFTR fromthe envelope of the RF signal, and generates a track cross directionsignal according to the phase relationship between the TKC and the OFTR,or generates a track cross detection pulse by directly using the TKC orby latching the TKC with the OFTR.

Reference numeral 114 denotes a rotation angle detection means fordetecting the rotation angle of the disc rotation means 103. Therotation angle detection means 114 generally utilizes a signal called anFG pulse that is generated from the output of a Hall element of a discmotor. As the FG signal outputs three pulses for one rotation with athree-phase motor, rotation angle detection in units of 60 degrees ispossible by counting both of a rising edge and a falling edge. Further,there are proposed a method of performing more accurate rotation angledetection by frequency-dividing the FG pulse, and a method of detectingthe rotation speed at an arbitrarily resolution by providing the discmotor with a rotation speed detection means using an encoder.

Reference numeral 115 denotes a count means for counting the number oftrack crosses including the direction, on the basis of the output fromthe rotation angle detection means 105, and the outputs from the trackcross detection means 112 and the track cross direction detection means113. In the above-mentioned case where the rotation angle can bedetected at every 60 degrees, one rotation is divided into six areas,and a signed track count is obtained for each area.

Reference numeral 116 denotes a control means for processing the signalssupplied from the conversion means 108 and the count means 115, andcontrolling the disc rotation means 103, the reading means 104, theconversion means 108, and the drive means 109.

Next, the operation will be described. Initially, a description will begiven of a step in which the control means 116 sets a maximum rotationspeed of the DVD-ROM player.

A step of detecting the track pitch of the optical disc 102 will bedescribed taking, for example, a method of determining the type of theinformation disc and selecting a standard track pitch according to theinformation about the disc type. Usually, the DVD-ROM player 101 canplay plural types of information discs as described above, and therequired light source and the method for generating a detection signalvary among the plural disc types. Therefore, initially, the type of theloaded disc is determined by various methods. For example, the loadedinformation disc is discriminated between a ROM (CD-ROM/R, DVD-ROM/R)disc and a rewritable disc (CD-RW), from the reflectivity of theinformation disc, using a CD laser, on the basis of the amplitude of afocus error signal obtained in focus search, and furthermore, it isdiscriminated between a DVD disc and a CD disc, from the degree ofmodulation of an RF signal, and thereafter, required light source andsignal path are selected. Finally, it is checked whether TOC (TABLE OFCONTENTS) information can be read from the disc or not, and further, itis checked whether the disc type selected from the contents of the TOCinformation is correct or not. Then, the standard value of the trackpitch according to the disc type is selected.

In a step of obtaining the result of counting by the count means whenthe disc is rotated at the first rotation speed, the drive means 104 isdisabled, and the optical disc 102 is rotated at the first rotationspeed by controlling the disc rotation means 103. Then, the result ofcounting by the count means 115 is captured. In this first embodiment,using a three-phase motor, utilizing an FG signal outputted from a Hallelement, the rotation angle is detected at the rising and falling edgesof the FG signal, and the counted number of track crosses is obtained atevery rotation angle of 60 degrees. Further, in this first embodiment,the first rotation speed is set at a sufficiently low speed which doesnot cause vibration between the reading means 104 and the optical disc102, and the number of track crosses caused by only the eccentricitybetween the optical disc 102 and the disc rotation means 103 ismeasured.

Also in a step of obtaining the count of the count means when theoptical disc 102 is rotated with at least one rotation speed that ishigher than the first rotation speed, the number of track crosses can becounted at every rotation angle of 60 degrees, as in the step ofobtaining the count of the count means when the disc is rotated at thefirst rotation speed. In this first embodiment, the count is obtained atthe maximum rotation speed that is set for every disc type of theDVD-ROM player.

Next, each of the counts obtained when the disc is rotated at the firstspeed and the at least one speed higher than the first speed ismultiplied by the track pitch which is detected in the track pitchdetection step, thereby obtaining data of the track cross amount. Inthis embodiment, data of the track cross amount at every 60 degrees iscalculated from the number of tracks counted at every rotation angle of60 degrees.

In a step of calculating the vibration amplitude of the optical disc 102with respect to the reading means 104, the track cross amount detectedat the first rotation speed is compared with the track cross amountdetected with the at least one rotation speed higher than the firstspeed, and the vibration amplitude of the information disc with respectto the reading means is calculated on the basis of a difference betweenthe track cross amounts. In this first embodiment, a difference betweenthe track cross amount detected at the first rotation speed and thetrack cross amount detected at the maximum rotation speed is obtained atevery rotation angle of 60 degrees, thereby calculating a track crosscomponent due to the vibration. Then, the vibration amplitude isobtained on the assumption that the vibration is a sinusoidal wave.

In a step of determining the maximum rotation speed, comparison iscarried out as to whether the previously obtained vibration amplitude islower than a reference value or not. When it is lower than the referencevalue, the maximum rotation speed that is set for every disc type isemployed, and when it is higher than the reference value, a rotationspeed lower than the maximum rotation speed is employed.

Then, reproduction of data is carried out at a speed lower than the setmaximum rotation speed.

Next, a description will be given of a case where vibration of a CD-ROMis to be detected.

A CD-ROM disc loaded on the DVD-ROM player 101 is fixed to the discrotation means 103. Next, focus search is carried out with a laser beamfor CD-ROM, and the amplitude of a focus error signal is measured. As aresult, the loaded CD-ROM disc is judged as a ROM disc because itsreflectivity is relatively high. Next, the CD-ROM disc is rotated at apredetermined speed by the disc rotation means 103, and the degree ofmodulation of an RF signal is measured. The measured degree of amplitudeis compared with a reference value, whereby the CD-ROM disc is judged asa CD disc, whereby the result of disc judgement is a CD-ROM. Also when aDVD-ROM disc is employed, the disc is judged as a DVD-ROM disc in thesame manner as described above, and then it is checked whether theDVD-ROM disc is a DVD-R4.7 G (track pitch: 0.74 μm) or a DVD-R3.9 G(track pitch: 0.8 μm) by reading the TOC information, whereby the trackpitch can be detected.

Next, the CD-ROM disc is rotated at a sufficiently low speed, 1200 rpm,which does not cause vibration between the disc and the reading means104. Then, the traverse drive means 110 and the tracking actuator 111are disabled, and the count of the count means 115 is obtained at everyrotation angle of 60 degrees. Since no vibration occurs between the discand the reading means 104, the count due to only the eccentricitycomponent between them is obtained. For example, the count may beobtained by a method of performing counting for plural rotations withone rotation as a unit, and averaging the obtained counts, or a methodof performing counting for plural rotations as described above, andselecting, from the obtained counts, plural counts which are notsupposed to be false counts.

Next, the CD-ROM disc is rotated at the maximum rotation speed of theCD-ROM disc. In this example, the CD-ROM disc is able to perform CAVplayback at 24× (maximum)-speed, 12×-speed, and 6×-speed. Since themaximum rotation speed is 5000 rpm, the 12×-speed is 2500 rpm, and the6×-speed is 1250 rpm, the count when the disc is rotated at 5000 rpm isobtained.

Next, a difference between the counts obtained at 1200 rpm and 5000 rpmfor every rotation angle is calculated, whereby the track count due tothe vibration at 500 rpm, excluding the eccentricity component, isobtained.

Finally, the vibration amplitude of this disc is evaluated from thistrack count and the track pitch, or the vibration speed or vibrationacceleration is evaluated from the track count, the track pitch, and therotation speed of 5000 rpm, and it is decided whether the disc is to berotated at the maximum rotation speed or not, according to whether thevibration amplitude, or the vibration speed, or the vibrationacceleration is lower than the allowable value or not. For example, whenit is higher than the allowable value, the maximum rotation speed isreduced to 2500 rpm of the 12×-speed.

As described above, according to the first embodiment, the vibrationamount, or vibration speed, or vibration acceleration is evaluatedconsidering the track pitch of the disc, and a maximum rotation speedthat is lower than the allowable vibration amplitude, or vibrationspeed, or vibration acceleration of the information discrecording/playback apparatus is decided. Therefore, vibration detectioncan be carried out using a single threshold value, independently of thetype of the information disc.

In this first embodiment, counting of the track crosses is carried outat plural rotation speeds while detecting the rotation angle, and adifference between them is calculated to obtain the track count due tovibration. However, there may be employed a method of simply countingthe track crosses at plural rotation speeds without detecting therotation angle and then taking a difference between them, or a method ofcounting the track crosses at a single rotation speed without detectingthe rotation angle.

Furthermore, while in this first embodiment evaluation of vibration isperformed on the basis of a difference between the count obtained at alow speed at which no vibration occurs and the count obtained at themaximum rotation speed, it may be performed on the basis of a differencebetween the count obtained at a rotation speed at which vibration occursand the count obtained at the maximum rotation speed. Further, not themaximum rotation speed but a rotation speed lower than the maximumrotation speed may be employed. Furthermore, evaluation may be carriedout at two or more rotation speeds, and the playback speed may be set asfollows: the maximum rotation speed, a speed lower than the maximumrotation speed, a speed lower than that speed, . . .

Moreover, in this first embodiment, the counted number of track crossesis multiplied by the track pitch to obtain data of the track crossamount, and the track cross amount due to vibration is calculated byoperating the track cross amount, and the vibration amplitude isobtained on the basis of the track cross amount due to vibration.However, as for the track pitch of the disc, the value of the trackpitch itself may be employed, or the ratio of track pitches of pluraldiscs may be employed. Furthermore, when the number of track crosses dueto vibration is obtained by operating the result of counting, the numberof track crosses may be multiplied by the track pitch to obtain thetrack cross amount due to vibration and, thereafter, the vibrationamplitude may be obtained. Alternatively, the vibration amount with thenumber of track crosses as a unit may be obtained, and the vibrationamount may be multiplied by the track pitch to obtain the vibrationamplitude.

Furthermore, while in this first embodiment the vibration amplitude isobtained and compared with a reference value, not the vibrationamplitude itself but a value in proportion to the vibration amplitude ora value in proportion to the second power of the vibration amplitude maybe calculated to be compared with the reference value. Further, thevibration speed or vibration acceleration may be obtained instead of thevibration amplitude.

While in this first embodiment detection of vibration of a CD-ROM discis described, vibrations of discs having different track pitches, suchas a DVD and a DVD-R3.9 G, can be detected in like manner as describedabove.

While in this first embodiment a DVD-ROM player capable of playingCD-ROM, DVD-ROM, DVD-R3.9 G, and DVD-R4.7 G is described as an example,any information disc player may be employed as long as it can playplural kinds of information discs having different track pitches.

Furthermore, while in this first embodiment a DVD-ROM player isdescribed as an example, the present invention is applicable to a casewhere a maximum recording speed at recording is set in other writablerecording/playback apparatuses such as CD-R, CD-RW, and DVD-R.

EMBODIMENT 2

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a second embodiment of the present invention willbe described, taking a DVD-ROM player as an example, with reference toFIG. 2.

In FIG. 2, the same reference numerals as those shown in FIG. 1 denotethe same or corresponding parts, and reference numeral 201 denotes atrack cross speed detection means for detecting a track cross speed onthe basis of the output from the track cross detection means 112.

The count means 115 counts the track count pulses while detecting thedirection when the track cross speed is lower than a predeterminedvalue, and counts the track count pulses without detecting the directionwhen the track cross speed is higher than the predetermined value, onthe basis of the output from the track cross speed detection means 201.When it is switched to “without direction detection”, the track crossdirection can be known on the basis of the direction obtained whencounting with direction detection has been most recently carried out.

The maximum speed at which track counting with direction detection canbe carried out depends on the track counting method or the disc type.

For example, when tracking error detection is carried out by thethree-beam method for a CD or by the phase difference method for a DVD,generally the three-beam method is able to perform direction detectionat a higher speed. Accordingly, a threshold value for determining as towhether track counting is to be carried out with direction detection ornot may be set for each disc type, or it may be set adaptively to a discof the lowest speed at which track counting with direction detection ispossible.

As described above, according to the second embodiment, the track crossspeed detection means 201 is provided, and the track counting method ischanged by detecting the track cross frequency. Therefore, even whendetection of the track cross direction is difficult because of thechange in the track cross speed, track counting can be performed withaccuracy, whereby accurate vibration detection can be performed at alltimes.

EMBODIMENT 3

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a third embodiment of the present invention willbe described, taking a DVD-ROM player as an example, with reference toFIGS. 3 and 6.

In FIG. 3, the same reference numerals as those shown in FIG. 1 denotethe same or corresponding parts, and reference numeral 301 denotes azero cross area detection means for detecting an area where the trackcross speed has the lowest value. The rotation angle detection means 114usually employs a signal called an FG pulse that is generated from theoutput of a Hall element of a disc motor. Since the FG signal outputsthree pulses for one rotation with a three-phase motor, rotation angledetection in units of 60 degrees can be carried out by counting both ofrising and falling edges. In this third embodiment, a description willbe given of a case where rotation angle detection is performed in unitsof 60 degrees using the FG pulses.

The zero cross area detection means 301 detects two areas each includinga position where the track cross speed has the lowest value. Forexample, there may be employed a method of detecting areas where thetrack cross speed has the lowest value by using the track cross speeddetection means 112, or a method of detecting, as zero cross areas, anarea where the absolute value of the track count has the lowest value,and an area on a diagonal line with respect to the area from among thesix-divided areas.

Hereinafter, a description will be given of the reason why the areawhere the absolute value of the track count has the lowest value and thearea on a diagonal line with respect to this area, among the six-dividedareas, are zero cross areas.

FIG. 6 is a graph illustrating the amount of displacement of the countby the count means 115 at every rotation angle, which displacement iscaused by vibration or eccentricity. A count DAT[n] in a zero cross areawithin a range of φ=0˜60°, which is a signed count obtained whenperforming direction detection, is represented byDAT[n]=T _(c) cos(φ)−T _(c) cos(φ−60)  (Formula 23)

Likewise, counts DAT[n+1] and DAT[n+2] in two areas which are not zerocross areas, within a range of φ=0˜60°, are represented byDAT[n+1]=T _(c) cos(φ+60)−T _(c) cos(φ)  (Formula 24)DAT[n+2]=T _(c) cos(φ+120)−T _(c) cos(φ+60)  (Formula 24)

A maximum value of |DAT[n]| within this range is represented by whenφ=0, 60°,|DAT[n]|=0.5T _(c)

Likewise, minimum values of DAT[n+1] and DAT[n+2] are represented by

-   when φ=0°,    |DAT[n+1]|=0.5T _(c)-   when φ=60°,    |DAT[n+2]|=0.5T _(c)

According, the following relationship always holds.|DAT[n]|≧|DAT[n+1],|DAT[n+2]|

Likewise, when the count is obtained without performing directiondetection, since only the number of track crosses is counteddisregarding the track cross direction, a count DAT[n] in a zero crossarea, within a range of φ=0˜60°, with cos(0) as a boundary, isrepresented byDAT[n]=|T _(c)(cos(0)−cos(φ))|+|T _(x)(cos(φ−60)−cos(0))|  (Formula 26)and, as in the above-described case of performing direction detection,counts in two areas which are not the zero cross areas are representedbyDAT[n+1]T _(c) cos(φ+60)−T _(c) cos(φ)  (Formula 27)DAT[n+2]T _(c) cos(φ+120)−T_(c) cos(φ+60)  (Formula 28)

A maximum value of |DAT[n]| within this range is represented by

-   when φ=0, 60°,    |DAT[n]|=0.5T _(c)

Likewise, minimum values of DAT[n+1] and DAT[n+2] are represented by

-   when φ=0°,    |DAT[n+1 ]|=0.5T _(c)-   when φ=60°,    |DAT[n+2]|=0.5T _(c)

According, also in this case, the following relationship always holds.|DAT[n]|≧|DAT[n+1], DAT[n+2]|

Next, an example of specific operation according to the third embodimentwill be described.

Initially, the optical disc 102 is rotated at a predetermined rotationspeed. After the traverse drive means 110 and the tracking actuator 111are disabled, the count of the count means 115 is obtained for everyrotation angle of 60 degrees. At this time, the count is obtained by anyof the following methods: a method of obtaining the count with directiondetection for an area which is judged as a zero cross area by the zerocross area detection means 301 while obtaining the count withoutdirection detection for other areas; a method of obtaining the countwith direction detection and the count without direction detectionseparately, and selecting the count with direction detection for thezero cross area while selecting the count without direction detectionfor other areas; and a method of obtaining the count with directiondetection and the count without direction detection at the same time,and selecting the count with direction detection for the zero cross areawhile selecting the count without direction detection for other areas.Further, an area that adopts the data without direction detection canobtain the same count as that with direction detection by adding thesign of a just previous area that adopts the data with directiondetection, or by adding the sign of a further previous area if the justprevious area adopts the data without direction detection.

As described above, according to the third embodiment of the presentinvention, since the zero cross area detection means 301 is provided,the track cross detection method is switched between the area where thetrack cross speed has the lowest value and the other areas, among theareas divided with the rotation angle obtained by the rotation angledetection means 114, and track counting is carried out with directiondetection for the area where the track cross speed has the lowest valuewhile it is carried out without direction detection for the other areas,whereby the optimum track counting method can be selected according tovariations in the track cross speed, and accurate vibration detectioncan be carried out at all times.

EMBODIMENT 4

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a fourth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 1.

Since the fundamental construction of the apparatus is identical to thatof the first embodiment, repeated description is not necessary. Next, anexample of specific operation of this fourth embodiment will bedescribed employing the rotation angle detection means 114.

A DVD-ROM disc loaded on the DVD-ROM player 101 is fixed to the discrotation means 103. Next, focus search is carried out with a laser forCD-ROM, and the amplitude of a focus error signal is measured. As aresult, the DVD-ROM disc is judged as a ROM disc because itsreflectivity is relatively high. Next, the DVD-ROM disc is rotated at apredetermined speed by the disc rotation means 103, and the degree ofmodulation of an RF signal is measured. The measured degree ofmodulation is compared with a reference value, whereby the disc isjudged as a DVD disc. Consequently, the disc judgement result is aDVD-ROM.

In this fourth embodiment, the DVD-ROM disc is able to perform 8×-speedplayback at 4590 rpm (maximum speed), 5×-speed playback at 2870 rpm, and2.5×-speed playback at 1435 rpm, and a low speed at which no vibrationoccurs is 1435 rpm. Vibration detection is carried out at 3000 rpm and4000 rpm, and it is judged whether or not the detected vibration amountsare lower than an allowable vibration amount at the 5×-speed and the8×-speed, respectively. Further, the allowable vibration amount is 100μm.

Initially, the DVD-ROM disc is rotated at 1435 rpm that is asufficiently low speed at which no vibration occurs between the disc andthe reading means 104. After the traverse drive means 110 and thetracking actuator 111 are disabled, the count of the count means 115 isobtained at every rotation angle of 60 degrees. Since no vibrationoccurs between the disc and the reading means 104, the count due to onlythe eccentricity component between the disc and the reading means 104 isobtained. For example, the count may be obtained by a method ofperforming counting for plural rotations with one rotation as a unit,and averaging the obtained counts, or a method of performing countingfor plural rotations as described above, and selecting, from theobtained counts, plural counts which are not supposed to be falsecounts.

For example, it is assumed that the data measured for four rotationswith direction detection in each of the six-divided areas, and theaverage of the measured data in each area are as follows: TABLE 1 countsat 1435 rpm No. area[0] area[1] area[2] area[3] area[4] area[5] 1 57 39−17 −57 −35 18 2 59 39 −20 −55 −35 18 3 57 37 −18 −57 −34 22 4 57 39 −18−59 −33 14 average 57.5 38.5 −18.3 −57.0 −34.3 18.0

Likewise, counting is carried out at 3000 rpm. When it is assumed thatthe counts at 3000 rpm are as follows: TABLE 2 counts at 3000 rpm No.area[0] area[1] area[2] area[3] area[4] area[5] 1 71 49 −21 −69 −48 18 271 49 −22 −69 −49 19 3 72 49 −22 −69 −49 18 4 72 51 −20 −71 −50 18average 71.5 49.5 −21.25 −69.5 −49 18.25

a difference between the @ average values of the track counts obtainedat 1435 rpm and 3000 rpm in each area is represented by TABLE 3 countsat 3000 rpm-1435 rpm DAT[0] DAT[1] DAT[2] DAT[3] DAT[4] DAT[5] 14.0 11.0−3.0 −12.5 −14.8 0.3and, these counts are track counts due to vibration.

In order to obtain the vibration amount from the data shown in (Table3), these data are substituted into (Formula 12) and (Formula 13),whereby 12 pieces of data are obtained as follows: TABLE 4 calculatedvibration amounts (3000 rpm-1435 rpm) vibration vibration vibrationvibration vibration vibration amount amount amount amount amount amount1[0] 1[1] 1[2] 1[3] 1[4] 1[5] 44 44 39 48 52 48 44 41 57 43 50 39

By averaging these 12 pieces of data, the vibration amount is obtainedas follows.

-   -   vibration amount=46 tracks

Further, since this disc is a DVD-ROM disc, the vibration amount ismultiplied by the track pitch of 0.74 μm, whereby the vibrationamplitude is obtained as follows.

-   -   vibration amplitude=34.04 [μm]

Since the allowable maximum vibration amount of the system is 100 μm andthe obtained vibration amplitude is lower than the allowable value, thedisc can be rotated at the 5×-speed, i.e., 2870 rpm.

Next, counting is carried out at 400 rpm. When it is assumed that thecounts at 4000 rpm are as follows: TABLE 5 counts at 4000 rpm No.area[0] area[1] area[2] area[3] area[4] area[5] 1 −61 86 133 53 −78 −1322 −62 86 132 53 −78 −133 3 −61 85 132 56 −78 −133 4 −62 82 133 56 −75−133 average −61.5 84.75 132.5 54.5 −77.25 −132.75

a difference between the average values of the track counts obtained at1435 rpm and 3000 rpm in each area is represented by TABLE 6 counts at4000 rpm-1435 rpm DAT[0] DAT[1] DAT[2] DAT[3] DAT[4] DAT[5] −119.0 46.3150.8 111.5 −43.0 −150.8and, these counts are track counts due to vibration.

In order to obtain the vibration amount from the data shown in (Table6), these data are substituted into (Formula 12) and (Formula 13),whereby 12 pieces of data are obtained as follows: TABLE 7 calculatedvibration amounts (4000 rpm-1435 rpm) vibration vibration vibrationvibration vibration vibration amount amount amount amount amount amount1[0] 1[1] 1[2] 1[3] 1[4] 1[5] 171 154 156 159 155 159 159 162 155 156168 154

By averaging these 12 pieces of data, the vibration amount is obtainedas follows.

-   -   vibration amount=159 tracks

Further, since this disc is a DVD-ROM disc, the vibration amount ismultiplied by the track pitch of 0.74 μm, whereby the vibrationamplitude is obtained as follows.

-   -   vibration amplitude=117.66 [μm]

Since the allowable maximum vibration amount of the system is 100 μm andthe obtained vibration amplitude is higher than the allowable value, thedisc cannot be rotated at the 8×-speed, i.e., 4590 rpm, and therefore,the maximum rotation speed is set at the 5×-speed.

Hereinafter, a description will be given of the reason why the vibrationamount, the vibration speed, and the vibration acceleration can beexpressed by (Formula 12)˜(Formula 17), using the signed counts obtainedwith direction detection.

When the track count area is divided into six sections at every 60degrees and counting is carried out for each section, the count in eachsection is represented by (Formula 29), assuming that the respectivesections are 0˜5, the vibration amount is Tc, and the phase angle of thetrack displacement amount at a starting point in section 0 is φ.DAT[n]=T _(c) cos(30n+φ)−T _(c) cos(30n+φ−60 )  (Formula 29)

When the data in the respective sections 0˜5 are DAT[0]=a, DAT[1]=b,DAT[2]=c, DAT[3]=−a, DAT[4]=−b, DAT[5]=−c, from (Formula 29), DAT[0] isrepresented by $\begin{matrix}{\begin{matrix}{{{DAT}\lbrack 0\rbrack} = {T_{c}\left( {{\cos(\phi)} - {\cos\left( {\phi - 60} \right)}} \right)}} \\{= {T_{c}\left( {{\cos(\phi)} - {{\cos(\phi)}{\cos(60)}} + {{\sin(\phi)}{\sin(60)}}} \right)}} \\{= {T_{c}\left( {{\frac{1}{2}{\cos(\phi)}} + {\frac{\sqrt{3}}{2}{\sin(\phi)}}} \right)}} \\{= {T_{c}{\sin\left( {\phi + \alpha_{1}} \right)}}}\end{matrix}{{Since}\quad\begin{matrix}{{{\sin\left( \alpha_{1} \right)} = \frac{\sqrt{3}}{2}},{{\cos\left( \alpha_{1} \right)} = \frac{1}{2}},} \\{\alpha_{1} = 60} \\{{\therefore{{DAT}\lbrack 0\rbrack}} = {T_{c}{\sin\left( {\phi + 60} \right)}}} \\{= a}\end{matrix}}} & \left( {{Formula}\quad 30} \right)\end{matrix}$Likewise, DAT[1] is represented by $\begin{matrix}{\begin{matrix}{{{DAT}\lbrack 1\rbrack} = {T_{c}\left( {{\cos\left( {\phi + 60} \right)} - {\cos(\phi)}} \right)}} \\{= {T_{c}\left( {{{\cos(\phi)}{\cos(60)}} - {{\sin(\phi)}{\sin(60)}} - {\cos(\phi)}} \right)}} \\{= {T_{c}\left( {{\frac{1}{2}{\cos(\phi)}} - {\frac{\sqrt{3}}{2}{\sin(\phi)}}} \right)}} \\{= {T_{c}{\sin\left( {\phi + \alpha_{2}} \right)}}}\end{matrix}{{Since}\quad\begin{matrix}{{{\sin\left( \alpha_{2} \right)} = {- \frac{\sqrt{3}}{2}}},{{\cos\left( \alpha_{2} \right)} = \frac{1}{2}},} \\{\alpha_{1} = {- 60}} \\{{\therefore{{DAT}\lbrack 1\rbrack}} = {T_{c}{\sin\left( {\phi - 60} \right)}}} \\{= b}\end{matrix}}} & \left( {{Formula}\quad 31} \right)\end{matrix}$From (Formula 30), $\begin{matrix}{{\sin\left( {\phi + 60} \right)} = \frac{a}{T_{c}}} & \left( {{Formula}\quad 32} \right)\end{matrix}$Then, (Formula 31) is represented by $\begin{matrix}{{\begin{matrix}{{{DAT}\lbrack 1\rbrack} = {T_{c}{\sin\left( {\phi + 60 - 120} \right)}}} \\{= {T_{c}\left( {{{\sin\left( {\phi + 60} \right)}{\cos\left( {- 120} \right)}} + {{\sin\left( {- 120} \right)}{\cos\left( {\phi + 60} \right)}}} \right)}} \\{= {T_{c}\left( {{{- \frac{1}{2}}{\sin\left( {\phi + 60} \right)}} - {\frac{\sqrt{3}}{2}{\cos\left( {\phi + 60} \right)}}} \right)}} \\{= {T_{c}\left( {{{- \frac{1}{2}}{\sin\left( {\phi + 60} \right)}} \mp {\frac{\sqrt{3}}{2}\sqrt{1 - {\sin^{2}\left( {\phi + 60} \right)}}}} \right)}} \\{= {{T_{c}\left( {{{- \frac{1}{2}}\frac{a}{T_{c}}} \mp {\frac{\sqrt{3}}{2}\sqrt{1 - \left( \frac{a}{T_{c}} \right)^{2}}}} \right)} = b}}\end{matrix}{{Accordingly},}}\quad} & \left( {{Formula}\quad 33} \right) \\{{{{{- \frac{1}{2}}a} \mp {\frac{\sqrt{3}}{2}\sqrt{T_{c}^{2} - a^{2}}}} = {{b \mp {\frac{\sqrt{3}}{2}\sqrt{T_{c}^{2} - a^{2}}}} = {b + {\frac{1}{2}a}}}}{{\frac{3}{4}\left( {T_{c}^{2} - a^{2}} \right)} = {b^{2} + {a\quad b} + {\frac{1}{4}a}}}{T_{c} = {{\pm \frac{2}{\sqrt{3}}}\sqrt{a^{2} + {a\quad b} + b^{2}}}}} & \left( {{Formula}\quad 34} \right)\end{matrix}$Likewise, since DAT[0]=a, DAT[2]=c, $\begin{matrix}{T_{c} = {{\pm \frac{2}{\sqrt{3}}}\sqrt{a^{2} - {ac} + c^{2}}}} & \left( {{Formula}\quad 35} \right)\end{matrix}$and, therefore, (Formula 12) and (Formula 13) are derived from (Formula34) and (Formula 35).

Furthermore, the track cross due to the eccentricity or vibration isrepresented by a sinusoidal wave as follows, using the Tc, phase angleφ, and angular velocity ω.f(t)=T _(c) cos(ωt+φ)  (Formula 36)Then, the absolute value of the track cross speed is obtained bydifferentiating (Formula 36) as follows. $\begin{matrix}{\left| \frac{\mathbb{d}{f(t)}}{\mathbb{d}t} \right| = \left. {\omega\quad T_{c}} \middle| {\sin\left( {{\omega\quad t} + \phi} \right)} \right|} & \left( {{Formula}\quad 37} \right)\end{matrix}$Since ω=2πf, and f=Vrpm/60 (Vrpm: present rotation speed [rpm]),$\begin{matrix}\begin{matrix}{\left| \frac{\mathbb{d}{f(t)}}{\mathbb{d}t} \right| = {2\pi\quad{fT}_{c}\text{|}{\sin\left( {{\omega\quad t} + \phi} \right)}\text{|}}} \\{= {\frac{2\pi\quad V_{rpm}}{60}T_{c}\text{|}{\sin\left( {{\omega\quad t} + \phi} \right)}\text{|}}}\end{matrix} & \left( {{Formula}\quad 38} \right)\end{matrix}$

Since (Formula 38) becomes maximum when|sin(ωt+φ)|=1  (Formula 39)(Formula 14) and (Formula 15) are derived from (Formula 34) and (Formula35), respectively.

Furthermore, the absolute value of the track cross acceleration isobtained by differentiating (Formula 38) as follows. $\begin{matrix}{\left| \frac{\mathbb{d}^{2}{f(t)}}{\mathbb{d}t^{2}} \right| = {\left( \frac{2\pi\quad V_{rpm}}{60} \right)^{2}\text{|}{\cos\left( {{\omega\quad t} + \phi} \right)}\text{|}}} & \left( {{Formula}\quad 4\quad 0} \right)\end{matrix}$Since (Formula 27) becomes maximum whencos(ωt+φ)=1  (Formula 41)(Formula 16) and (Formula 17) are derived from (Formula 34) and (Formula35), respectively.

As described above, according to the fourth embodiment of the presentinvention, when the vibration amplitude, or vibration speed, orvibration acceleration is evaluated considering the track pitch of theoptical disc 102, it is calculated at every predetermined rotation angleand an average of the results of calculation is obtained, and a maximumrotation speed that is lower than the allowable vibration amplitude, orvibration speed, or vibration acceleration of the information discrecording/playback apparatus is determined on the basis of the average.Therefore, vibration detection can be carried out more accurately ascompared with the first embodiment, using a single threshold value,independently of the type of the information disc.

While in this fourth embodiment, setting of the maximum rotation speedof the DVD-ROM disc is described, the maximum rotation speeds of othertypes of discs having different track pitches, such as a CD-ROM dischaving a track pitch of 1.6 μm or a DVD-R3.9 G disc having a track pitchof 0.8 μm, can also be obtained by judging as to whether the measuredmaximum vibration amount is lower than the allowable one, using thestandard track pitch of each disc and the vibration amount.

Further, while in this fourth embodiment the vibration amount isobtained on the basis of the average of 12 pieces of data, the vibrationamount may be obtained using the average of m pieces of central valuesselected from the 12 pieces of data which are arranged in the order ofsize, or using a value in proportion to the average.

Furthermore, while in this fourth embodiment the maximum playback speedis set on the basis of the vibration amplitude, the maximum playbackspeed may be set using a value in proportion to the vibration amplitudeor a value in proportion to the second power of the vibration amplitude.Alternatively, the maximum playback speed may be set on the basis of thevibration speed or a value in proportion to the vibration speed or thesecond power of the vibration speed, using (Formula 14) and (Formula 15)as well as the disc rotation speed. Further, the maximum playback speedmay be set on the basis of the vibration acceleration speed or a valuein proportion to the vibration acceleration speed or the second power ofthe vibration acceleration speed, using (Formula 16) and (Formula 17) aswell as the disc rotation speed.

Moreover, while in this fourth embodiment the maximum playback speed isset on the basis of the data obtained for four rotations each rotationbeing divided into six areas, the maximum playback speed may be obtainedby measuring data corresponding to continuous two or more areas.

EMBODIMENT 5

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a fifth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 4.

In FIG. 4, the same reference numerals as those shown in FIG. 1 denotethe same or corresponding parts, and reference numeral 116 a denotes acontrol means having a linear speed detection means 401 and a playbackspeed detection means 402. The linear speed detection means 401 detectsthe linear speed of the disc. For example, the linear speed is detectedas follows. An address value at a certain radial position is previouslyread, one-track jumping is carried out, an address value at thedestination of the track jumping is read, and a difference between theaddress values is obtained as the linear speed. Alternatively, thelength of one rotation of the disc is obtained from a radial position,and the linear speed of the disc is obtained on the basis of the radioof the length to the difference between the previously obtained addressvalues for one rotation. The playback speed detection means 402 detectsthe current playback speed. For example, the current playback speed isobtained from the cycle of a PLL which generates a data playback clock,or it is obtained on the basis of the cycle of a frame clock which isoutputted for every frame of data.

Next, a description will be given of the operation for obtaining thetrack pitch.

Generally, assuming that the track pitch of the disc is Tp, the linearspeed is V1, the current address position is Ad, the current radialposition is r, the radial position at the innermost radius is R0, andthe address value included in the unit time is Adunit, the followingrelationship holds. $\begin{matrix}{\frac{\pi\left( {r^{2} - R_{0}^{2}} \right)}{T_{p}} = \frac{V_{1}{Ad}}{{Ad}_{unit}}} & \left( {{Formula}\quad 42} \right)\end{matrix}$

Further, assuming that the current rotation speed is Vrpm, the playbackspeed V2 at the radial position r is represented by $\begin{matrix}{V_{2} = {\frac{2\pi\quad r}{V_{1}}\frac{V_{rpm}}{60}}} & \left( {{Formula}\quad 43} \right)\end{matrix}$

Therefore, assuming that the linear speed is V1, the current addressvalue is Ad, and the current rotation speed is Vrpm, the track pitch Tpis represented by $\begin{matrix}{T_{p} = {{\pi\left\lbrack {\left( \frac{60V_{1}V_{2}}{2\pi\quad V_{rpm}} \right)^{2} - R_{0}^{2}} \right\rbrack}\frac{{Ad}_{unit}}{V_{1}{Ad}}}} & \left( {{Formula}\quad 44} \right)\end{matrix}$

Accordingly, the track pitch Tp can be obtained by further measuring thecurrent playback speed V2 at a certain address Ad.

Although the address Ad at which the current playback speed V2 isobtained may be an arbitrary address, when measurement is carried out atan outer radial position, the accuracy is improved.

For example, assuming that a CD-ROM disc has

-   -   linear speed V1=1.25 m/s    -   playback speed measurement address AD=60:00:00    -   =270000 [frame]    -   rotation speed=5300 rpm    -   playback speed=23.8×        according to the standard of CD-ROM,    -   Adunit=75 [frame]    -   R0=0.0249 [m]        are obtained, and these values are substituted into (Formula 44)        to obtain the track pitch as follows.    -   Tp=1.573 [μm]

As described above, according to the fifth embodiment, when a movedistance detection means for detecting the move distance of the readingmeans 104 is provided, accurate vibration detection can always becarried out by measuring the accurate track pitch, even when the trackpitch is different from the standard value that is set for each disctype. Furthermore, when the track pitch is obtained from the linearspeed, address value, and playback speed, accurate vibration detectioncan always be carried out by measuring the accurate track pitch, evenwhen the track pitch is different from the standard value that is setfor each disc type, with reduced cost, without the necessity of adding amove distance detection means.

While in this fifth embodiment the track pitch of a CD-ROM disc isobtained, the track pitches of discs based on other standards, such as aDVD or a DVD-R3.9 G, can be obtained in like manner as described above.

Further, while in this fifth embodiment the track pitch is obtained fromthe linear speed, address value, and playback speed, the track pitch maybe obtained as follows. As shown in FIG. 10, the control means 116 b isprovided with a move distance detection means 403 for detecting the movedistance of the reading means 104, and the reading means 104 is movedwhile counting the number of tracks, and the track pitch is obtained asfollows.

-   -   Tp=move distance/number of crossed tracks

EMBODIMENT 6

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a sixth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 5.

In FIG. 5, the same reference numerals as those shown in FIG. 1 denotethe same or corresponding parts, and reference numeral 501 denotes avariable filter means having a function of shaping the track crosspulses detected by the track cross detection means 112 so that thepulses whose widths are narrower than a predetermined value, among thedetected pulses, are not counted.

Hereinafter, a method of actually setting the variable filter means 501will be described.

When setting the variable filter means 501, initially, the total numberof track crosses for one or more rotation is counted by the method inwhich the track cross direction is not detected. At this time, it isnecessary to set an initial set value of the variable filter means 501,and usually, this initial value must be set at such a value that theminimum track count pulse width corresponding to the maximum track crossspeed is surely counted when an eccentricity between the disc and theturn table and a maximum vibration amplitude estimated at its rpm occur.

Assuming that the counted number of track crosses is 4Tc per rotation,the maximum track cross speed can be obtained as follows.

Initially, the track cross due to the eccentricity or vibration isexpressed by a sinusoidal wave. Using the above-mentioned Tc, phaseangle φ, and angular velocity ω, the track cross is represented byf(t)=T _(c) cos(ωt+φ)  (Formula 45)

Then, the absolute value of the track cross speed is obtained bydifferentiating (Formula 32) as follows. $\begin{matrix}{\left| \frac{\mathbb{d}{f(t)}}{\mathbb{d}t} \right| = \left. {\omega\quad T_{c}} \middle| {\sin\left( {{\omega\quad t} + \phi} \right)} \right|} & \left( {{Formula}\quad 46} \right)\end{matrix}$Since ω=2πf, and f=Vrpm/60 (Vrpm: current rotation speed [rpm]),$\begin{matrix}\begin{matrix}{\left| \frac{\mathbb{d}{f(t)}}{\mathbb{d}t} \right| = {2\pi\quad{fT}_{c}\text{|}{\sin\left( {{\omega\quad t} + \phi} \right)}\text{|}}} \\{= {\frac{2\pi\quad V_{rpm}}{60}T_{c}\text{|}{\sin\left( {{\omega\quad t} + \phi} \right)}\text{|}}}\end{matrix} & \left( {{Formula}\quad 47} \right)\end{matrix}$

Accordingly, the maximum track cross speed is represented by$\begin{matrix}{{{maximum}\quad{track}\quad{cross}\quad{speed}} = {\frac{2\pi\quad V_{rpm}}{60}T_{c}}} & \left( {{Formula}\quad 48} \right)\end{matrix}$and, the maximum track cross speed can be obtained from the value of Tc.

The minimum track count pulse width is calculated on the basis of themaximum track cross speed. Assuming that the maximum track cross speedis Vmax[tracks/s], as two positive/negative pulses are outputted pertrack, the minimum track count pulse width is represented by$\begin{matrix}{{{minimum}\quad{track}\quad{count}\quad{pulse}\quad{width}} = {\frac{1}{2V_{\max}}\lbrack s\rbrack}} & \left( {{Formula}\quad 49} \right)\end{matrix}$Thereby, the minimum track count pulse width of the variable filtermeans 501 is set. For example, when the total number of counted tracksper rotation at 3000 rpm is 287, the maximum track cross speed isrepresented as follows:

Initially, since

-   -   Tc=287/4=71.75        and, from (Formula 18),    -   Vmax=22.54 kHz        and, therefore, the minimum track count pulse width is 22.18 μs        from (Formula 49).

The variable filter means 501 is set on the basis of this value so thatpulses whose widths are narrower than the minimum track count pulseobtained by the above calculation are also counted, consideringvariations in the duty ratio of the normal pulse width, or the like.

In this sixth embodiment, the variable filter means 501 is set so that apulse having a width of up to 5.54 μs, which is one fourth of 22.18 μs,is counted as a track cross signal.

During high-speed driving, the duty ratio of the track count pulse mightsignificantly vary due to an influence of vibration in the focusingdirection, a reduction in the amplitude level of the detection signalfor track counting, or the like. In this case, the variable filter means501 may be set so that a pulse having a narrower width is counted ifdriving at a speed higher than a predetermined value is expected, whilein the above example a value obtained by dividing the calculated minimumtrack count pulse width by a predetermined value is employed as a setvalue of the filter means 501.

When the track counting is performed by the method in which a signedcount is outputted because direction detection is carried out, thecalculation method is somewhat different from that mentioned above. Forexample, in the system of outputting rotation angle information obtainedby dividing one rotation into six areas, assuming that the count in eacharea for one rotation isDAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5]

-   -   (when n>5, n=n mod 6 (a remainder of n being divided by 6), the        maximum track cross speed becomes as represented by (Formula 19)        or (Formula 20). Thereby, data of plural maximum track cross        speeds are obtained, and the minimum track count pulse width may        be set similarly by using the average of these data, or the        average of m pieces of central values of these data, or the        like.

As described above, according to the sixth embodiment of the presentinvention, setting of the track cross filter by the variable filtermeans 501 is carried out on the basis of the track cross count and thecurrent rpm, so that the pulses whose widths are narrower than apredetermined value are not counted. Therefore, even when the trackcross speed varies significantly due to the eccentricity or vibration ofthe disc, track counting most suitable for vibration detection can beaccurately carried out at all times.

Furthermore, setting of the minimum track count pulse width may becarried out only once before obtaining the track count for detecting thevibration amount at each rotation speed, or it may be carried out everytime the data (count) for detecting the vibration amount is obtained.

EMBODIMENT 7

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a seventh embodiment of the present inventionwill be described taking a DVD-ROM player as an example, with referenceto FIGS. 5 and 6.

Usually, a general purpose microcomputer having a relatively small sizeis employed as a control means for computer peripheral equipment such asa DVD-ROM player. Such microcomputer is basically adaptive to integerarithmetic only, and therefore, floating-point arithmetic or square roottrigonometric function must be dealt with by software.

In the calculation formula (Formula 19) or (Formula 20) which isemployed when the track counting is carried out by the method in which asigned count is outputted because direction detection is carried out asdescribed for the sixth embodiment, it is necessary to obtain squareroots, resulting in a problem that the number of program steps and thetime required for arithmetic are increased in the system as describedabove. Therefore, in this case, assuming thatDAT[n]=DAT[0], DAT[1], DAT[2], DAT[3], DAT[4], DAT[5](when n>5, n=n mod 6 (a remainder of n being divided by 6), and therotation speed of the disc rotation means is Vrpm[rpm], $\begin{matrix}{{4T_{c}} = {{{{DAT}\lbrack 0\rbrack}} + {{{DAT}\lbrack 1\rbrack}} + {{{DAT}\lbrack 2\rbrack}} + {{{DAT}\lbrack 3\rbrack}} + {{{DAT}\lbrack 4\rbrack}} + {{{DAT}\lbrack 5\rbrack}}}} & \left( {{Formula}\quad 50} \right) \\{{{maximum}\quad{track}\quad{cross}\quad{speed}} = {{\frac{2\pi\quad V_{rpm}}{60}T_{c}\frac{1}{\cos\quad\frac{\pi}{6}}} = {\frac{2\pi\quad V_{rpm}}{60}T_{c}\frac{2}{\sqrt{3}}}}} & \left( {{Formula}\quad 51} \right)\end{matrix}$and, therefore, the maximum track cross speed can be calculated withreduced number of program steps and reduced arithmetic time, and thevariable filter means can be set on the basis of the maximum track crossspeed.

This is explained as follows with reference to FIG. 6.

FIG. 6 is a graph illustrating the amount of displacement of the countat every rotation angle, which displacement is caused by vibration oreccentricity.

Initially, the track cross due to eccentricity or vibration is expressedas a sinusoidal wave, in like manner as described for the sixthembodiment. Using the Tc, phase angle φ, and angular speed ω, the trackcross is represented by $\begin{matrix}{{\sin\left( {\phi + 60} \right)} = \frac{a}{T_{c}}} & \left( {{Formula}\quad 52} \right)\end{matrix}$

Then, this is divided at every 60 degrees by dividing one rotation intosix sections, as shown in FIG. 6. In FIG. 6, 601 shows a waveform whenφ=0, and 602 shows a waveform when φ=30°.

For example, when φ=0, assuming that the data corresponding to 0˜60°,60˜120°, 120˜180°, . . . are DAT[0], DAT[1], DAT[2], . . . ,respectively, the respective data are represented as follows.$\begin{matrix}{{{{DAT}\lbrack 0\rbrack} = {{T\left( {{\cos(60)} - {\cos(0)}} \right)} = {{- \frac{1}{2}}T_{c}}}}{{{DAT}\lbrack 1\rbrack} = {{T_{c}\left( {{\cos(120)} - {\cos(60)}} \right)} = {- T_{c}}}}{{{DAT}\lbrack 2\rbrack} = {{T_{c}\left( {{\cos(180)} - {\cos(120)}} \right)} = {{- \frac{1}{2}}T_{c}}}}{{{DAT}\lbrack 3\rbrack} = {{T_{c}\left( {{\cos(240)} - {\cos(180)}} \right)} = {\frac{1}{2}T_{c}}}}{{{DAT}\lbrack 4\rbrack} = {{T_{c}\left( {{\cos(300)} - {\cos(240)}} \right)} = T_{c}}}{{{DAT}\lbrack 5\rbrack} = {{T_{c}\left( {{\cos(360)} - {\cos(300)}} \right)} = {\frac{1}{2}T_{c}}}}} & \left( {{Formula}\quad 53} \right)\end{matrix}$

In this case, the Tc calculated from (Formula 21) becomes the same asthe original value of the Tc.

However, in the case where the boundary of the areas divided at every 60degrees as described above does not agree with the position where thetrack move direction is inverted (in the case of the waveform 601 whenφ=0, the position 603 or 604), the Tc calculated by (Formula 21) becomessmaller than the original Tc, and the calculated maximum track crossspeed also becomes lower than the original value. When the Tc takes thesmallest value, the waveform and divided-area as shown by 602 areobtained when φ=−30°. At this time, the respective data are representedas follows. $\begin{matrix}{{{{DAT}\lbrack 0\rbrack} = {{T\left( {{\cos(30)} - {\cos\left( {- 30} \right)}} \right)} = 0}}{{{DAT}\lbrack 1\rbrack} = {{T_{c}\left( {{\cos(90)} - {\cos(30)}} \right)} = {{- \frac{\sqrt{3}}{2}}T_{c}}}}{{{DAT}\lbrack 2\rbrack} = {{T_{c}\left( {{\cos(150)} - {\cos(90)}} \right)} = {{- \frac{\sqrt{3}}{2}}T_{c}}}}{{{DAT}\lbrack 3\rbrack} = {{T_{c}\left( {{\cos(210)} - {\cos(150)}} \right)} = 0}}{{{DAT}\lbrack 4\rbrack} = {{T_{c}\left( {{\cos(270)} - {\cos(210)}} \right)} = {\frac{\sqrt{3}}{2}T_{c}}}}{{{DAT}\lbrack 5\rbrack} = {{T_{c}\left( {{\cos(330)} - {\cos(270)}} \right)} = {\frac{\sqrt{3}}{2}T_{c}}}}} & \left( {{Formula}\quad 54} \right)\end{matrix}$

Therefore, the Tc calculated from (Formula 21) becomes 0.866 times theoriginal Tc. Accordingly, when the track counting is carried out by themethod in which a signed count is outputted because direction detectionis carried out, a value smaller than the original Tc, i.e., 0.866 timesthe original Tc at the worst, is calculated. Considering this effect,when calculating the maximum track cross speed on the basis of the Tccalculated from (Formula 21), (Formula 22) represents the maximum trackcross speed including the expected error.

As described above, according to the seventh embodiment, the maximumtrack cross speed including an expected error is calculated on the basisof the signed track cross count and the current rpm, and the track crossfilter is set on the basis of the maximum track cross speed. Therefore,track counting most suitable for vibration detection can be accuratelycarried out at all times, without necessity of performing additionalcounting without signs or calculating square roots which require manyprogram steps.

EMBODIMENT 8

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to an eighth embodiment of the present inventionwill be described taking a DVD-ROM player as an example, with referenceto FIG. 5. The fundamental construction is identical to that shown inFIG. 5 and, therefore, the distinctive operation of this eighthembodiment will be mainly described hereinafter.

When setting the variable filter means 501, initially, the total numberof track crosses for one or more rotation is counted by the method inwhich the track cross direction is not detected. At this time, it isnecessary to set an initial set value of the variable filter means 501,and usually, this initial value must be set at such a value that theminimum track count pulse width corresponding to the maximum track crossspeed is surely counted when an eccentricity between the disc and theturn table and a maximum vibration amplitude estimated at its rpm occur.

Assuming that the counted number of track crosses is 4Tc per rotation,the maximum track cross speed is represented by (Formula 55), using theTc, phase angle φ, and angular velocity ω. $\begin{matrix}{{{maximum}\quad{track}\quad{cross}\quad{speed}} = {\frac{2\pi\quad V_{rpm}}{60}T_{c}}} & \left( {{Formula}\quad 55} \right)\end{matrix}$

On the basis of this maximum track cross speed, the minimum track countpulse width is calculated. Assuming that the maximum track cross speedis Vmax [tracks/s], since two positive/negative pulses are outputted pertrack, the minimum track count pulse width is represented by$\begin{matrix}{{{minimum}\quad{track}\quad{count}\quad{pulse}\quad{width}} = {\frac{1}{2V_{\max}}\lbrack s\rbrack}} & \left( {{Formula}\quad 56} \right)\end{matrix}$and the minimum track count pulse width of the variable filter means 501is set according to the above formula.

Further, setting the minimum track count pulse width is carried outevery time the data (count) for performing detection of the vibrationamount is obtained. When the value of the minimum track count pulsewidth varies by a predetermined value or more at the same rotationspeed, there is a high possibility of false track counting of theprevious counts because an optimum track count filter has not been set,and therefore, the value of the minimum track count pulse width isdiscarded, and only the counts after the change should be adopted as thecounts for vibration detection.

As described above, according to the eighth embodiment, the countsobtained before the set value of the variable filter means 501 haschanged by a predetermined value or more are not used because thepossibility of false counting is high. Therefore, track counting mostsuitable for vibration detection can be accurately carried out at alltimes.

EMBODIMENT 9

Hereinafter, an information disc recording/playback apparatus and avibration detection method for the information disc recording/playbackapparatus according to a ninth embodiment of the present invention willbe described taking a DVD-ROM player as an example, with reference toFIG. 7.

In FIG. 7, the same reference numerals as those shown in FIG. 1 denotethe same or corresponding parts, and reference numeral 701 denotes apulse width storage means for holding the width of a pulse that is justprevious to the current pulse. Reference numeral 702 denotes a filtermeans which receives the track cross pulse outputted from the trackcross pulse detection means 112, and outputs it to the count means 115.At this time, the pulse width is measured, and when the measured pulsewidth is a predetermined value smaller than the pulse width stored inthe pulse width storage means 702, this pulse is regarded as one due tofalse count and is not outputted.

As for the amount of change in the pulse width that is not counted, themeasured pulse width should not be counted when it becomes smaller thanthe just-previous pulse width by a predetermined ratio, for example,0.5.

As described above, according to the ninth embodiment of the presentinvention, the pulse width storage means 701 and the filter means 702are provided, and when the filter means 702 judges that the measuredpulse width is a predetermined value smaller than the just-previouspulse width which is stored in the pulse width storage means 701, thispulse is regarded as one due to false detection caused by noise and isnot counted by the count means 115. Therefore, track counting mostsuitable for vibration detection can be accurately carried out at alltimes, without requiring time for excessive measurement.

APPLICABILITY IN INDUSTORY

An information disc recording/playback apparatus and a vibrationdetection method for the information disc recording/playback apparatusaccording to the present invention are valuable as an information discrecording/playback apparatus having a vibration measurement means formeasuring vibrations caused by eccentricity of a disc, and a vibrationdetection method for the information disc recording/playback apparatus,and particularly, the apparatus and method are valuable as those havinga construction for detecting vibrations using track counting.

1. An information disc recording/playback apparatus capable of recordingor playing an information disc on which information recording tracks areformed spirally or concentrically, said apparatus comprising: a discrotation means for rotating the information disc at a predeterminedspeed; a reading means for reading an information signal from the disc;a drive means for driving the reading means in the direction of theradius of the disc; a track cross detection means for generating trackcross signals on the basis of playback signals that are generated whenthe reading means crosses the information tracks; a pulse width storagemeans for holding the pulse width of a just-previous track cross signal;a filter means for comparing the pulse width of the just-previous trackcross signal with the pulse width of the current track cross signal, andpreventing the current track cross signal from being outputted when thecurrent track cross signal is reduced by a predetermined value or more;a count means for counting the pulses which are outputted from thevariable filter means; and a control means for determining a maximumrotation speed that is lower than an allowable number of track crossesof the information disc recording/playback apparatus on the basis of theobtained counts for one or more rotation, or determining a maximumrotation speed that is lower than an allowable track cross speed ortrack cross acceleration of the information disc recording/playbackapparatus on the basis of the obtained counts for one or more rotation,and the current disc rotation speed, and controlling the disc rotationmeans so that the disc rotation means rotates the information disc at aspeed lower than the allowable maximum rotation speed to record orreproduce data in/from the disc.
 2. An information discrecording/playback apparatus as defined in claim 1, wherein saidinformation disc recording/playback apparatus is able to record or playtwo or more kinds of information discs having different track pitches;and setting of the maximum rotation speed of the information discrecording/playback apparatus is performed by detecting the track pitchof the information disc, and determining a maximum rotation speed thatis lower than an allowable vibration amplitude of the information discrecording/playback apparatus on the basis of the count and the trackpitch, or determining a maximum rotation speed that is lower than anallowable vibration speed or vibration acceleration of the informationdisc recording/playback apparatus on the basis of the count, the trackpitch, and the current disc rotation speed.
 3. A method for detectingvibrations of an information disc recording/playback apparatus capableof recording or playing an information disc on which informationrecording tracks are formed spirally or concentrically, said methodcomprising: a step of counting track cross pulses on the basis ofplayback signals which are generated when the information disc fixedlyloaded on the apparatus is rotated and a reading unit crosses theinformation tracks on the information disc, thereby obtaining a count; astep of storing the pulse width of a track cross pulse which has justpreviously been detected; a step of comparing the stored track crosspulse width with the pulse width of the current track cross pulse, andinvalidating the count of the current track cross pulse when its pulsewidth is decreased by a predetermined value or more; a step ofdetermining a maximum rotation speed that is lower than an allowablenumber of track crosses of the information disc recording/playbackapparatus, on the basis of the count; and a step of determining amaximum rotation speed that is lower than an allowable track cross speedor track cross acceleration, on the basis of the count and the currentdisc rotation speed.